Documents

• 1: Protection
• 1.1: DIY Residential PAPR
• 1.1.1: Materials
• 1.1.2: License
• 1.2: Powered Respirator
• 1.2.1: Materials
• 1.3:
• 2: Organizing

1 - Protection

1.1 - DIY Residential PAPR

DIY Residential PAPR

Overview

Industrial PAPRs can provide clean air with very low breathing resistance. However, most PAPRs are heavy, noisy, and expensive. What if a lightweight “residential” PAPR for home and office use can deliver the same level of clean air for a fraction of the weight, noise, and cost?

This DIY PAPR attaches to your N95 (or better) to lower breathing resistance, eliminate moisture (whether in humid or cold weather), while increasing overall filtration efficiency without the noise, weight, or cost of an industrial/commercial PAPR. The device pairs with a source-controlled N95 to protect the people around you, and it’s constructed from replaceable parts, so it’s easy to repair.

“Residential PAPR” has a nice symmetry when shortened to “rPAPR” and hints at a lighter (but still tremendous) protection level that can be worn at home, the office, concerts, and parties. It can also be worn to the dentist when combined with a ReadiMask.

Check out these fit scores.

For comparison, the typical 3M Aura (N95) registers 200-300 fit factor on the PortaCount 8020A

DIY PAPR + Drager X-Plore 1950 M/L (2 Weeks Old)
NIOSH test	Fit factor	FF (Unpowered)
Normal Breathing	394000	247
Deep Breathing	379000	327
Left right	377000	326
Up down	123000	328
Grimace	119000	184
Talk (Whisper only)	10800	150
Bend	344000	396
Normal Breathing	415000	405
Overall	65428	264

(Fit factor is a measure of how much cleaner air is inside the mask than outside, by particle count.)

In the event that the device loses power, it still protects. The unpowered rPAPR extends the N95 and filters passively even when the blower is off.

This design uses 3M bayonet filters, which have excellent quality control, performance, variety, and availability. Most hardware stores carry them.

This design has adjustable flow: low for the office and at home, and high for exercise. Shown below are the case internals, with battery and voltage adjustment.

Want to get “industrial?” You can connect the rPAPR to a Honeywell North 7700 Series half mask respirator for source control! (Instructions at the end.)

It’s also worth mentioning that powered masking has reduced the friction for masking uptake among kids.

Very often, only KN95-level protection is available for toddlers, but when combined with a powered filter like the rPAPR, their protection level can be brought up to an adult’s.

But how does it feel?

In my day to day, this setup has replaced all masking setups whether indoors or outdoors. I no longer keep separate masks for separate scenarios. It’s simply the most breathable mask setup I have. On days below freezing, moisture doesn’t build. I can stay comfortable masking all day, even at the mandatory full day in the office.

Discussion on fit test results

When fit testing friends with the rPAPR, the results are lower for deep breathing. Deep breathing overcomes the clean air delivery rate of the blower, bringing the masking efficiency to baseline. You can think of your lungs as a high capacity bellows. Industrial PAPRs must blow at high levels to handle the few cases where you have to breathe deep.

DIY PAPR + JedX FFP3	5.3 v	6.0 v
NIOSH test	FF	FF
Normal Breathing	114000	435000
Deep breathing	448	940
Left/Right	30300
Up/Down	4890
Grimace	84600
Talking	385	889
Bending	134000
Normal breathing	31600
Overall	1560

Talking alters the dynamics of the rPAPR in a similar way. In order to talk, we take in gusts of air that’s similar to deep breathing. The whisper-only talking test attempts to control for this and test only the effects of the mouth and jaw movements.

Even then, we can see a reduction in the fit score. These can be attributed to the seal of the mask. The 10,000-or-so fit score seen in the first table is still impressive, yet it may indicate micro-compromises in the seal that is “patched” by the positive pressure inside of the mask.

All this to say that the results are highly dependent on having a good, well sealing N95. Bifold KN95 masks don’t fare as well. On its highest setting, the best the rPAPR can do is to get it up to 3M Aura levels. For many, this is a considerable improvement. For most, however, just wearing the 3M Aura would be a lot less trouble and expense.

We have found that increasing the flow rate helps restore some of the filtration efficiency that’s “lost” when deep breathing. For physical activity like dance classes, it’s worth dialing up the input voltage to 5.7 v or 6.0 v.

Table of Contents

Safety Disclaimer

The following instructions are provided as-is and free of charge for informational purposes only. The author assumes no responsibility or liability for any issues, damages, losses, or injuries that may result from the construction, use, misuse, or inability to use this device or these instructions. This includes, but is not limited to, health effects, exposure to fumes or materials, mechanical failure, electrical hazards, or unintended consequences of operation. The device is used entirely at your own risk. No guarantees are made regarding safety, performance, completeness, or suitability for any particular purpose. Users are responsible for ensuring proper materials, safe construction practices, adequate ventilation, and compliance with all applicable laws, regulations, and safety standards. The author is not responsible for errors, omissions, or changes in conditions, materials, or user capability. By using these instructions, you acknowledge and accept full responsibility for all outcomes related to the device.

Materials and Cost

Refer to the Materials Page for a breakdown of materials, costs, and suppliers.

There are two columns for cost: individual and bulk. In most if not all cases, you can only buy in bulk. The individual column is provided for those who want to make multiple rPAPRs, and to provide a cost estimate for commissions.

Adhesives are listed in the bulk column only.

Batteries are the most expensive component, and as of 2026/2/16, prices are skyrocketing. I’m researching use of 18650 cells, but at this point I can’t recommend any alternatives.

Tools

• Power drill and bits
  • Drill bits
  • Step drill bit
• Rotary tool with cutting blades
• Soldering iron
• Automatic wire stripper (manual not recommended)
• Scissors
• Adjustable wrench
• Box cutter
• Screwdriver
• PortaCount 8020A

Optionally:

• 13 mm hole punch (for quickly installing the hose adapter to the N95)
• Rubber mallet
• Sewing kit (If sewing on the D-ring attachments for the strap)

Detailed Instructions

Use these instructions to make your own rPAPR.

These instructions only cover the exposed version of the rPAPR:

However, a “sheltered” version can be constructed, which faces the filter inward, towards the body. To make this, a thicker pouch is needed, available here.

The differences between these two variants:

	Exposed	Sheltered
Nominal Voltage	5.3 v	5.7 v
Battery Life	8 hours	6 hours
Filter replacement	Easy	Cumbersome
Filter type	All 3M bayonet filters	Only pancake filters

In lieu of making the sheltered variant, you can use a filter cover for the exposed variant can be constructed.

This is a difficult build. You will need power tools, soldering, and precision. Care must be taken to properly seal the blower unit which sits inside the case. Some electronics knowledge is needed.

To test the rPAPR, you will need a particle counter, such as the PortaCount 8020A.

Select the Filter

The blower unit must be tested at several points in the build using a PortaCount. It’s helpful to commit to a filter type early so you can have one on hand for your tests.

Filter Name	Characteristics
3M 2071 - “Blue Pancake”	The highest air flow. Decent filtration efficiency. Lowest profile.
3M 2291 - “White pancake”	Good balance of air flow and very high filtration efficiency.
3M 2297 - “Gray pancake”	Same as above with a carbon layer for nuisance level organic vapor.
3M 2091 - “Pink pancake”	Wider availability, but lower air flow than the 2291. Same filtration efficiency.
3M 2097 - “Pink pancake”	Same as above with a carbon layer for nuisance level organic vapor.
3M 7093 - Cartridge	Okay air flow. Lowest measured filtration efficiency. Cannot be used in the sheltered version.
3M 7093c - Cartridge	Same as above with a carbon layer for nuisance level organic vapor.

In normal conditions, the pancake filters outshine the pleated cartridges thanks to the electret material, which helps to filter below 0.3 micron. However, this advantage disappears when wetted (and reappears when dry, since as the name implies, the electret is like a magnet but for electric charge). For rainy, humid, or oily conditions, the 7093 cartridges are better, albeit at much lower baseline filtration efficiency because of the non-charged mechanical nature of the pleated filtration media. Generally speaking, use the pancakes for indoor use, and cartridges for outdoor use.

Maintenance: Filters must be changed when flow rate gets low, about twice a year or more for home and office use.

Avoid touching the filter material. If contact is a concern, consider either the 7093/7093c, or using a filter cover. Alternatively, the “sheltered” version of this build faces the filter towards the body and hides it inside the case.

Make the hose fittings

Use a rotary tool, Dremel, or saw to remove the non-threaded half of 2x thru-bulk hose fittings. These fittings form both ends of the intake hose. One fitting will be used for the rPAPR’s hose adapter. The other will be installed inside the mask.

Refer to this page for more detailed info.

Make the Blower Unit

Select blower type

For this build, I suggest a sleeve bearing 7515 blower unit for:

• Lower noise (very important)
• Lower cost

However, you may choose a ball-bearing 7515 unit for:

• Longevity for higher cost.
• Reduced vibration but higher noise.

Refer to the materials page for my recommended supplier of 7515 blower. This blower supplier has been selected for giving me the fewest duds with regard to the vertical mount chatter problem. Your mileage may vary.

Cut the USB cable

Cut and strip the cable. Recommended slack: at least 75 mm (3 inches) on the blower side and USB side.

For the sheltered variation, this slack is needed so that the blower wire can reach the boost converter. (In the sheltered version, the boost converter is mounted to the hinge side of the unit.)

The above wire was stripped of its outer sheath in seconds using the auto wire cutter.

Test the blower

This build uses a boost converter to maintain steady voltage with a small cost to battery life. This also makes the air flow adjustable for your needs, and ensures even airflow delivery throughout the charge cycle of the battery.

Without a boost converter, airflow can weaken as the battery loses charge.

5.3V Minimum recommended for good air flow and 8 hours of battery.

6V Maximum rated over-voltage for most 7515s. Higher protection, higher airflow, and about 6 hours of battery.

Attach the power source

The battery listed on the materials page is rated for 5V DC, 2.4 A, 5000 mah/18.5 Wh. This build has only been tested with this power rating. Use any other power rating at your own risk.

That said, one advantage of the boost converter is that you can use a wide variety of input voltages. There’s nothing theoretically wrong with using a battery with a different rating from above.

Attach the USB power source to the boost converter. Dial the boost converter to 5.3 V. Disconnect the battery.

Attach the blower to the circuit, using the screws, ensuring correct polarity. Red wires connect to terminal designated with a plus (+) sign, and black wires connect to terminal designated with a minus (-) sign.

Reconnect the battery.

Ensure that air is blowing

Adequate air flow is approximately 6 CFM.

Test for chatter

The shaft of the sleeve-bearing fan is supported by a thin oil film inside a porous bushing. That oil film is happiest when the load is steady and the shaft stays centered.

When you mount the fan vertically (shaft horizontal) and then move it sideways, a few things line up to make the rotor “snap” into a noisy state. Lubricating oil on the sleeve bearing catches and resonates, causing chatter. This is always present to some extent, but in some fan units, it’s particularly loud and annoying. It’s best to test this phenomenon before you proceed further with the project.

Test Steps:

With the battery connected, hold the blower upright and turn the body quickly left or right.

If the chatter is too loud, reserve the blower for use in another project and buy another blower, or go with a ball-bearing 7515 (with trade-off of a persistent high-pitched whine).

Make the blower enclosure

We’ll use a 85 x 85 x 30 mm polyethylene clear case for the enclosure, as they’re cheap, widely available, crack resistant, and easily drilled and worked. The drawback is that you can’t seal polyethylene with most types of glue. This will be addressed in the sealing step.

Clear polyethylene is also needed for you to inspect the adhesion of the blower enclosure’s components for bubbles and air leaks. That said, if you prefer an easier time sealing, then an ABS or polypropylene case is theoretically possible. (I couldn’t find one.)

The supplier of this clear case was chosen for quality, cost, and exact dimensions. Don’t deviate here, as all measurements are for this specific case from this specific supplier only.

Orient the enclosure

Before we proceed, we need to establish a convention for referring to the sides of the unit.

Designate the side of the hinge on the clear case as North. The side with the clasp is South. The lid is “top” and the side at the bottom of the container is “bottom.” West and East must be inferred, but if you and the case are facing North, West is to your left and East is to your right.

Drill the ports

3 holes are needed:

Adapter port

• 26 mm diameter, centered on the lid.
• Drill using the step drill bit.
• Tip: alternate drilling from both inside and outside.

Hose port

• 15 mm diameter. Located west, 2 cm from north, centered between top and bottom.
• Drill using the step drill bit.

Wire port

• 2 mm diameter. Located at the bottom, centered between east and west, and about 3 mm from south.

The hose and adapter port are easily made using a step-drill bit. The holes can be marked with a scratch awl.

Tip: If you’ll be making many of these, then make and use a drill guide from spare wood.

Finished enclosure body:

Working with poster putty

At several points in this build, thin and even strands of poster putty are needed. This can be achieved by twisting the putty between the thumb and index finger into a thicker, wobbly baguette of roughly 4 mm diameter, and then pulling both ends to the desired thickness. This aligns the polymer strands of the poster putty and results in a strong, thin strand of uniform thickness. This is especially important in sealing step for the rim of the enclosure.

Attach the hose fitting

The hose fitting is sealed by poster putty. Stretch a 2 mm thick strand of poster putty around the outer flange of the hose fitting, and fit it into the western port with hand pressure.

Attach the filter adapter

We have selected the Omnimask 3M filter adapter for its low profile and low cost. While official 3M adapters work, they cost more, protrude by an inch, and aren’t very fashionable.

Repair the older Omnimask filter adapter

The older filter adapters have 3 spokes with an orange gasket. These have loose play on the bayonet connector column. Newer filter adapters (6 spokes with a clear gasket) do not have this problem.

To repair the older adapter, remove the gasket seal and put a ring of poster putty around the base. Install the gasket and connect a filter. This squeezes the putty to a thin layer that raises the gasket enough to restore the seal.

(Pictures are from an older build that uses paper mache for the sealing step.)

Cut an adhesive ring

Using a 3M double sided mounting pad (40 mm / 1.57 inch diameter), trace and cut a hole corresponding to the size of the enclosure’s adapter port.

Orient the filter adapter

For aesthetic reasons, this step is recommended even if you intend to use this blower unit with the radially symmetric filters.

Orient the filter adapter by attaching it to a 3M 7093 filter. Align the filter how you would like. I suggest orienting the side that’s away from the filter’s attachment port to the west.

Install the filter adapter

Remove the paper backing and apply to the filter adapter.

Remove the red adhesive backing and apply to the adapter port of the enclosure.

If you left a sacrificial tab as suggested above, trim it off with some craft scissors.

Inspect the adhesion for air leaks. Be suspicious of air bubbles. If a path between the inner and outer edge of the ring is detected, you must start over. Because we are using polyethylene, do-overs are easy. Even the most tenacious mounting tape can be removed.

If you used the 7093 to orient the filter adapter, you may now detach it.

Noise reduction

We will use layers of cardboard for stability and noise reduction. Cardboard reduces noise by directing sound waves into its corrugated channels, where waves cancel out. (Mufflers work on the same principle.) Layering the cardboard enhances this effect.

Cut the noise panels

Cut out four 78 mm squares of single layered cardboard. We use 78 mm to simplify the fitting on the lid, and to provide clearance from the hose port when the cardboard is fully inlaid.

Of 4 squares, two require a centered hole for the filter adapter. The holes are graduated in size between the filter adapter port and the blower intake.

Recommended hole diameters: Inner lid noise panel: 48 mm Outer lid noise panel: 36 mm

From top to bottom:

• Outer lid noise panel
• Inner lid noise panel
• Inner bottom noise panel
• Outer bottom noise panel

Panels are layered with corrugations running orthogonally.

Insert the noise panels

Insert the noise panels:

Divots have been cut out for the hose adapter base:

Additionally, cut out divots for the wire through-hole.

Install the blower

Thread the wire into the wire through-hole. Place the blower as shown and pack it with cardboard.

There should be some bulge on the sides due to the uncompressed ring of putty on the hose port.

Squeeze the east and west sides to check the amount of give. If there’s too much, support with more cardboard. We need to minimize give. Once the putty ring is compressed, this give will increase. Too much case flex may compromise the seal.

Close the enclosure

Close the enclosure.

Compress inner putty ring

Install the nut and use a wrench to turn the nut on the hose port. This creates pressure that squeezes out the inner poster putty to form a seal.

Unscrew the retaining nut and visually inspect for bubbles. Set the retaining nut aside.

Test for chatter again

Because of changes to the acoustic dynamics of the blower, an enclosed blower can surface issues with vibration.

Attach the boost converter circuit, and then attach the USB power bank. Check for chatter as per this section.

Seal the case

This is the most time consuming and difficult part of the build.

Seal the hose port

Lay a strand of poster putty at base of the adapter hose thread.

Screw the nut back in, applying torque, and squeezing the putty out to the sides. Don’t turn the nut all the way. If you do, it will sheer the putty, compromising one level of the seal. Instead, turn until it’s about 2 mm from the west side.

Use the scratch awl or a toothpick to pack in the space with poster putty until flush with the edges of the nut.

Seal the lid

The clear case uses polyethylene. Glue will NOT stick to the case, and will peel when flexed. This includes super glue like cyanoacrylate.

Instead, we will seal with poster putty, and then put a barrier around the poster putty to protect it.

Lay a strand of poster putty around the seam where the lid meets the container. Remember, poster putty can be stretched thin by kneading in a twisting motion, and then pulling apart. For tips, check this section.

Press the putty into place.

Seal the putty

What makes poster putty so good at ceiling polyethylene also makes it fragile for everyday wear and tear. We’ll be sealing the poster putty to harden it from the outside.

We can do so in a way that introduces a second level of air seal.

Cloth tape was chosen for its ability to conform to the geometry of the object it’s taping. The tape must hug the poster putty without introducing bubbles or air channels (after the tape is sealed).

By contrast, non-woven tape such as PVC tape and polyurethane have been tried, and these introduce air channels which drop the filtration efficiency of the unit significantly, so their function as a secondary seal is not fulfilled.

Seal the wire through-hole

Use poster putty to seal the wire through-hole.

Two strands are needed: around both wires, and between the wires.

Press it down into place.

Using a toothpick or scratch awl, apply pressure until the putty goes through the wire port and is visible on the inside of the enclosure.

Measure and cut a strap of cloth tape

Tape all the way around the putty. The adhesive adheres strongly to the putty, and this part can’t be undone. The tape adheres weakly to the polyethylene but the edges will be distant from the seam, ensuring a good seal.

Note how the tape hugs the geometry of the putty seal.

Reinforce and waterproof the tape using wood glue. This also waterproofs the seal.

Wood glue was chosen for its combination of being waterproof, easy to work with, strong, and fairly cheap and easy to obtain. (As with most PVA glues, check your sensitivity. One alternative is to seal with shellac, which the cloth tape will wick just fine.) This also prevents the seepage of adhesive over time, as the blower should be useful in all weather conditions.

Brush the glue onto the tape. Make sure to get the edges. A disposable nail polish brush can be used.

Here’s the finished unit that goes into the case

Optional: paper mache

If you can devote an entire day to the sealing step, you can opt to use Paper Mache.

Tape the lid closed using masking tape.

The masking tape will help the paper mache grip the polyethylene.

Make a paper mache paste from dilute wood glue (about 3:1 glue to water).

Tear off small bits of paper and seal the enclosure.

Test the seal

Connect the hose and attach a filter.

Connect the boost converter. Connect the battery.

Connect the sample tube, and disconnect the ambient air tube. This causes the fit score to be calculated with respect to the position of ambient intake port, not the ambient tube. Next, place the filter as close to the ambient intake as possible. This will give a more accurate measure of the nominal filtration efficiency, or fit score.

Run a single exercise, ensuring ambient particles are above 2000 per cubic milliliter.

The nominal filtration efficiency with 3M 2091 filters should be on the order of 100,000 to 999,000. If it’s less, there may be a leak.

Troubleshooting a low FF can be difficult. The most common source of leaks is forgetting to seal the wire through-hole, since it’s tiny and on the underside of the blower enclosure. Furthermore, check that you have a functioning filter adapter, and that you haven’t missed any of the sealing steps.

Make the carrying case

A carrying case is needed to mount the blower unit to you and hold the battery.

The carrying case should be lightweight, weather resistant, and adjustable.

Only instructions for the exposed variant are provided. For the sheltered variant, you may look at the pictures and infer the proper construction.

Orient the case

We have to name the sides so that the zipper pull closes to the righthand side, away from the hose.

Point the side with the zipper up. This is the top. The opposite side is the bottom.

Zip the zipper all the way closed. The side with the zipper pull in the closed position is the right.

The opposite side where the zipper started is the left.

Orient the case so that the left and right correspond to your left and right.

The side away is the front. The side nearest is the back. This is important: the front of the case is where the filter attaches, and in the exposed variant, it will face away from you.

Orient the blower enclosure to the case

Line up the blower unit with the case so that the blower unit’s north side (as per the enclosure orientation) faces the case’s bottom, ensuring that the zipper pull in the closed zipper position is on the right side, with “bottom” and “right” defined above.

The case and unit properly oriented:

This will be the ironclad orientation for the blower unit with respect to the case, for the rest of this build.

Cut the port holes

Insert the blower unit with the proper orientation, and press it against the case left. Mark the center where the hose port presses against the case left. Use this mark to cut a 20 mm hole for the hose port.

Once cut, insert the hose port, and mark the center for the adapter port. Cut an 8-point star shape that is 30 mm wide, so that the adapter port fits snugly.

Attach the strap

On the back at the top of the case, mount the strap on the left and right side.

Options for mounting the straps:

• Punch 4 holes and grommets, and thread the strap loops through.
• Sew a set of D-rings and thread the strap loops through.

The above also shows the back of the sheltered case variant. Note the grommet holes for airflow.

Use any adjustable strap that you like. A cheap one is suggested on the Materials Page.

Make the filter cover

This is optional.

This filter cover allows you to wipe down the surface for safe handling. Be advised that alcohol vapors may compromise filtration media.

You can also paint the filter cover for aesthetics.

The filter cover is not waterproof.

Make the stencil

Draw and cut a circular stencil.

Stencil measurements

	# Holes	Radius
Center	1	0 mm
1st Ring	8	18 mm
2nd Ring	16	38 mm
Perimeter		54 mm

Drill the holes

Tape to the jar lid (see the Materials page) and drill the holes.

Drilling must be graduated and begin with a small drill bit. Too much force will crack the lid. Work up to a desired size using the step drill bit.

Line the inner rim

A spacer is needed to prevent the filter from contacting the cover. This allows air flow.

Cut a 11 mm x 335 mm strip of cardboard. Line the inner rim with the cardboard.

Attach retaining wire

The retaining wire locks the cover to the filter.

To make the retainer, drill hours on the side, about 60 degrees apart (or 110 mm * pi / 6 ~ 60 mm). Thread in some medium gauge electric wire, tie, and then trim. Wire must overhang the rim.

The completed cover

Final Assembly

Solder the USB connector

To supply battery power from the side opposite of the boost converter, we won’t be using the built-in USB ports.

Instead, solder the dangling USB port created in this step to the positive and negative input terminals of the boost converter.

Attach the boost converter

Attach the boost converter to the blower unit on the south side, with the USB-A port facing west. Use a combo of poster putty and masking tape.

For setting the boost convert, see the section on Testing the Blower.

Don’t use electrical tape – you’ll regret it.

Attach the hose

The hose is attached when flush against the retaining nut. The double barbs will not damage the soft silicone.

Ensure that both barbs are secure and that the hose will not come loose.

Secure the hose using about 15 cm (6 inches) of X-Fasten silicone tape.

Thread the blower unit into the case

Tape the adapter port so that debris doesn’t get inside during this step. Thread the hose through the case left. Thread the adapter port through the case front. Note the star shape formed by the seated adapter port.

(Case is shown upside down)

Put all the electronics inside. The angle adapter allows all the components to fit inside.

Fit the battery into the space on the case right with the USB port facing case top. Attach the blower unit USB port to the USB angle adapter. Attach the USB angle adapter to the battery.

Install the filter cover

This is optional.

To install the cover, wedge the edge of the filter pancake between the wire retainer and cardboard spacer. Pull the other wire retainer over the edge on the opposite side.

Connect to N95

Refer to this page for how to Attach to your N95 Mask

While it’s recommended to attach to the chin of a boat style N95, we’ve found that some folks are much more comfortable with the hose attached to the side of their mask. For bifold KN95s, this is mandatory. Do not attach over a seam since this significantly alters the fit.

And with that, the build is complete!

Use the rPAPR

Power the device

Connect the battery. If nothing comes on, press the button the battery by the LED charge indicator. Check the voltage readout on the boost converter. If it reads zero, then press the on/off button on the boost converter, located near the read out.

The typical battery life of this design is 8 hours on medium flow (5.3 v), and 6 hours at high flow (5.7 v). For a full day at the office, you can keep a spare battery swap it out halfway through.

The battery may be swapped out without taking the mask off, since a well-sealed mask continues to protect during an unpowered state, as shown in the overview.

Put it on

The unit goes over the right shoulder

Adjust the strap

Adjust the strap.

A shorter strap increases the slack of the hose. When mounted, fully turn your head to the left, right, and upward. Check for tugging on the connection point to the mask, and tugging on the hose.

Tugging on the hose compromises safety by lifting/tugging on the connection point to your mask, compromising the seal. If you intend to use the mask for dance classes, concerts, or parties, the unit must be secured close to the center of your chest.

Don the mask

Put on your mask normally.

Enjoy your residential PAPR

And there it is!

The rPAPR in action:

Bonus: connect to a half mask respirator

You can use your residential PAPR with a half mask elastomeric respirator for source control.

Moisture is the typical problem seen in source-controlled elastomerics.

To make this work, you have to remove the valve flaps. Elastomerics typically have three of them, two for the filters on inhale, and one for exhale.

Next you have to find an attachment point that covers the exhale.

The Honeywell North 7700 series is great for this, because you can easily remove the exhale valve, turn it around, reinstall it, and secure a acrylic disk with a hole drill through it for the hose. A picture are provided without detailed instructions.

License

This work is licensed under the CERN Open Hardware Licence Version 2 - Permissive (CERN-OHL-P-2.0).

You may use, modify, and distribute this design, including for commercial purposes, provided that you retain attribution to the original author.

Full License Here

2/18/2026 – v1.0.1

1.1.1 - Materials

All prices are approximate in USD. These prices are for estimating the cost, and only represent a snapshot. Prices are subject to change without notice. Parts availability will change without notice.

Main respirator unit

The individual cost column is provided only for the purpose of charging commissions. In most if not all cases, you can only buy in bulk.

Item	Cost	Bulk Cost	Where to buy
5 V USB Battery	$16.50	$32.99	https://a.co/d/06VIqs1z
7515 Blower unit	$8.99	$8.99	https://a.co/d/2ifYiF5
Clear container	$1.58	$18.95	https://a.co/d/1uDZMCK
Broad FB2 air hose	$5.00	$5.00	https://broadfreshair.com/products/air-hose-16-inches
90 degree USB adapter	$5.00	$9.99	https://a.co/d/5Z70ppT
Thru-bulk bulkheads (2x)	$5.99	$8.99	https://a.co/d/1RqXWmk
Boost converter	$2.50	$14.99	https://a.co/d/ec15Eht
Filter adapter	$6.65	$19.95	https://www.omnimask.com/products/omnimask-filter-adapters
3M 2291 Filters	$5.23	10.45	https://a.co/d/03iX60hC
Parts Sub Total	$52.20	$119.85
Sales Tax	$3.59	$8.24
Total	$55.79	$128.09

Note on batteries

We are researching ways to lower this costs and deliver safety as well as performance.

Protective cover

Item	Cost	Bulk Cost	Where to buy
110mm Black Plastic Lids	$2.25	$9.00	https://a.co/d/04Nnn7vS
22 Gauge Wire

Case

Item	Cost	Bulk Cost	Where to buy
Pouch	$6.99	$6.99	https://a.co/d/hih6PlX
Shoulder strap	$3.20	$15.99	https://a.co/d/1fuTbBh
1/4 inch grommets and tool		$9.99	https://a.co/d/0h0L3cCN
D rings		$9.99	Optional: https://a.co/d/03hCEeBQ
Parts Sub Total	$10.19	$42.96
Sales Tax	$0.70	$2.95
Total	$10.89	$45.91

Adhesives

Adhesives	Cost	Where to buy
Wood Glue	$5.97	https://a.co/d/0dawLZon
Poster Putty	$6.97	https://a.co/d/0aqgt5oG
Cloth Tape	$7.19	https://a.co/d/02e6x0MP
3M mounting pads	$17.99	https://a.co/d/07OReSHq
X-Fasten Silicone Tape	$14.99	https://a.co/d/07w14jZL
Sub Total	$53.11
Sales Tax	$3.65
Total	$56.76

Totals

	Commission	DIY + Adhesives
Parts Total	$66.68	$230.76
Labor (10 hours x fed min wage)	$72.50	N/A
Commission Cost	$139.18

The federal minimum wage is used to calculate the labor cost, and does not represent a sustainable rate.

1.1.2 - License

CERN Open Hardware Licence Version 2 - Permissive

Preamble

CERN has developed this licence to promote collaboration among hardware designers and to provide a legal tool which supports the freedom to use, study, modify, share and distribute hardware designs and products based on those designs. Version 2 of the CERN Open Hardware Licence comes in three variants: this licence, CERN-OHL-P (permissive); and two reciprocal licences: CERN-OHL-W (weakly reciprocal) and CERN-OHL-S (strongly reciprocal).

The CERN-OHL-P is copyright CERN 2020. Anyone is welcome to use it, in unmodified form only.

Use of this Licence does not imply any endorsement by CERN of any Licensor or their designs nor does it imply any involvement by CERN in their development.

1 Definitions

1.1 ‘Licence’ means this CERN-OHL-P.

1.2 ‘Source’ means information such as design materials or digital code which can be applied to Make or test a Product or to prepare a Product for use, Conveyance or sale, regardless of its medium or how it is expressed. It may include Notices.

1.3 ‘Covered Source’ means Source that is explicitly made available under this Licence.

1.4 ‘Product’ means any device, component, work or physical object, whether in finished or intermediate form, arising from the use, application or processing of Covered Source.

1.5 ‘Make’ means to create or configure something, whether by manufacture, assembly, compiling, loading or applying Covered Source or another Product or otherwise.

1.6 ‘Notice’ means copyright, acknowledgement and trademark notices, references to the location of any Notices, modification notices (subsection 3.3(b)) and all notices that refer to this Licence and to the disclaimer of warranties that are included in the Covered Source.

1.7 ‘Licensee’ or ‘You’ means any person exercising rights under this Licence.

1.8 ‘Licensor’ means a person who creates Source or modifies Covered Source and subsequently Conveys the resulting Covered Source under the terms and conditions of this Licence. A person may be a Licensee and a Licensor at the same time.

1.9 ‘Convey’ means to communicate to the public or distribute.

2 Applicability

2.1 This Licence governs the use, copying, modification, Conveying of Covered Source and Products, and the Making of Products. By exercising any right granted under this Licence, You irrevocably accept these terms and conditions.

2.2 This Licence is granted by the Licensor directly to You, and shall apply worldwide and without limitation in time.

2.3 You shall not attempt to restrict by contract or otherwise the rights granted under this Licence to other Licensees.

2.4 This Licence is not intended to restrict fair use, fair dealing, or any other similar right.

3 Copying, Modifying and Conveying Covered Source

3.1 You may copy and Convey verbatim copies of Covered Source, in any medium, provided You retain all Notices.

3.2 You may modify Covered Source, other than Notices.

  You may only delete Notices if they are no longer applicable to
  the corresponding Covered Source as modified by You and You may
  add additional Notices applicable to Your modifications.

3.3 You may Convey modified Covered Source (with the effect that You shall also become a Licensor) provided that You:

   a) retain Notices as required in subsection 3.2; and

   b) add a Notice to the modified Covered Source stating that You
      have modified it, with the date and brief description of how
      You have modified it.

3.4 You may Convey Covered Source or modified Covered Source under licence terms which differ from the terms of this Licence provided that You:

   a) comply at all times with subsection 3.3; and

   b) provide a copy of this Licence to anyone to whom You
      Convey Covered Source or modified Covered Source.

4 Making and Conveying Products

You may Make Products, and/or Convey them, provided that You ensure that the recipient of the Product has access to any Notices applicable to the Product.

5 DISCLAIMER AND LIABILITY

5.1 DISCLAIMER OF WARRANTY – The Covered Source and any Products are provided ‘as is’ and any express or implied warranties, including, but not limited to, implied warranties of merchantability, of satisfactory quality, non-infringement of third party rights, and fitness for a particular purpose or use are disclaimed in respect of any Source or Product to the maximum extent permitted by law. The Licensor makes no representation that any Source or Product does not or will not infringe any patent, copyright, trade secret or other proprietary right. The entire risk as to the use, quality, and performance of any Source or Product shall be with You and not the Licensor. This disclaimer of warranty is an essential part of this Licence and a condition for the grant of any rights granted under this Licence.

5.2 EXCLUSION AND LIMITATION OF LIABILITY – The Licensor shall, to the maximum extent permitted by law, have no liability for direct, indirect, special, incidental, consequential, exemplary, punitive or other damages of any character including, without limitation, procurement of substitute goods or services, loss of use, data or profits, or business interruption, however caused and on any theory of contract, warranty, tort (including negligence), product liability or otherwise, arising in any way in relation to the Covered Source, modified Covered Source and/or the Making or Conveyance of a Product, even if advised of the possibility of such damages, and You shall hold the Licensor(s) free and harmless from any liability, costs, damages, fees and expenses, including claims by third parties, in relation to such use.

6 Patents

6.1 Subject to the terms and conditions of this Licence, each Licensor hereby grants to You a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable (except as stated in this section 6, or where terminated by the Licensor for cause) patent licence to Make, have Made, use, offer to sell, sell, import, and otherwise transfer the Covered Source and Products, where such licence applies only to those patent claims licensable by such Licensor that are necessarily infringed by exercising rights under the Covered Source as Conveyed by that Licensor.

6.2 If You institute patent litigation against any entity (including a cross-claim or counterclaim in a lawsuit) alleging that the Covered Source or a Product constitutes direct or contributory patent infringement, or You seek any declaration that a patent licensed to You under this Licence is invalid or unenforceable then any rights granted to You under this Licence shall terminate as of the date such process is initiated.

7 General

7.1 If any provisions of this Licence are or subsequently become invalid or unenforceable for any reason, the remaining provisions shall remain effective.

7.2 You shall not use any of the name (including acronyms and abbreviations), image, or logo by which the Licensor or CERN is known, except where needed to comply with section 3, or where the use is otherwise allowed by law. Any such permitted use shall be factual and shall not be made so as to suggest any kind of endorsement or implication of involvement by the Licensor or its personnel.

7.3 CERN may publish updated versions and variants of this Licence which it considers to be in the spirit of this version, but may differ in detail to address new problems or concerns. New versions will be published with a unique version number and a variant identifier specifying the variant. If the Licensor has specified that a given variant applies to the Covered Source without specifying a version, You may treat that Covered Source as being released under any version of the CERN-OHL with that variant. If no variant is specified, the Covered Source shall be treated as being released under CERN-OHL-S. The Licensor may also specify that the Covered Source is subject to a specific version of the CERN-OHL or any later version in which case You may apply this or any later version of CERN-OHL with the same variant identifier published by CERN.

7.4 This Licence shall not be enforceable except by a Licensor acting as such, and third party beneficiary rights are specifically excluded.

1.2 - Powered Respirator

Overview

This cost-effective PAPR (powered air purifying respirator) typically scores between 1,000 to 6,000 on my PortaCount 8020, which corresponds to a filtration efficiency of 99.98%. By comparison, a fit score of 200 is typical for the popular 3M Aura 9205+, which is considered high enough for use in health care settings. Anything over 500 will put you in rarefied air, as it were.

Powered Air Purifying Respirators (PAPRs) offer a significant advantage in respiratory protection by providing lower breathing resistance, exceptional filtration efficiency, and positive air pressure, which prevents contaminants from entering the mask even in the presence of leaks.

This build has completely changed my life, allowing me to comfortably wear a mask during exercise, and for much longer than before. I have helped people move while masked. I can feel confident about my protection in crowded places. The mask breathes so well that I don’t need a separate setup for use outdoors.

Use these instructions to create your own lightweight PAPR.

The Broad AirPro

This build is based off of the Broad AirPro, a lightweight and budget-friendly PAPR suitable for most residential/commercial settings. Off the shelf, however, the unit has leaks. Without modifications, it achieves a fit score of around 40, far below the standard required for effective protection.

The HEPA filters that come with the unit, however, are H13 rated, a very high filtration efficiency. To fully realize this potential, modifications are necessary.

Plug the leaks

Refer to these instructions to plug up the leaks of the Broad AirPro and achieve the full filtration efficiency that the unit is capable of.

There are a few major sources of leakage that allow unfiltered air to enter the chamber. These leaks were found using the PortaCount 8020. Every one of them must be plugged.

Please refer to the materials page for a complete list of materials and costs.

Power Button

Cover the power button with a square of 3M Nexcare Blister Prevention Tape. This tape is chosen for its flexibility and water-resistance.

Any flexible and water-resistant tape will work for this mod.

Charging Port

The charging port must be permanently covered. We will use a magnet charging adapter that fits into the micro USB port. This allows you to close off the air to the port and charge the battery.

Start by installing the magnetic charging adapter.

---

Lay a strip of poster putty around the adapter. Using a combination of finger pressure and toothpicks, smush the putty against the adapter and case to form a seal.

Alternatively, hot glue may be used. For maintenance, hot glue can be removed using a dash of isopropyl alcohol.

Here is the unit with charging cable attached:

LED Panel

The tiny holes for the LED panel must be covered. These holes make a very big difference on fit tests. Cover the LED panel with Scotch Heavy Duty Shipping Tape, or any tape with good visual clarity.

It’s important to keep the tape inside the oval. Any tape that hangs over the edge of the oval can be levered off by pressing on it, and invites the ingress of oil/grease which will dissolve the adhesive. If you have a hard time cutting and applying a small piece of tape, consider using clear nail polish.

Battery Cover

Even though the cracks look thin, the battery cover is a major source of leakage.

We can seal this leak using tape. We will use blue masking tape for demonstration purposes. Instead, you should use packing tape, or any airtight tape for your build. The tape must be thin, or else overlapping tape creates a channel for air leakage.

Electrical tape is not recommended. Over time, heat melts the electrical tape causing black sludge to seep out of the edges.

---

Lay a strip of tape across the top of the battery cover, with about 1/4 inch of overhang. Press the sides down.

---

Surround the sides of the battery cover in tape.

---

Cut off the excess tape.

For a smoother look, you can take the tape off and then flip it so that machine edge lines up with the case edge.

The battery cover is now sealed.

PCB

If the other leaks are plugged, then this is optional. I still recommend taking this step as a failsafe to ensure that air takes a direct route from the filter to the blower.

Pop open the front cover and take out the HEPA filter.

Lay down stretches of poster putty, starting with the edges. Do not cover the black gasket seal.

Lay down more putty until the PCB is fully covered.

Using a combo of finger pressure, a smooth pen cap, and a toothpick, shape the putty to close off gaps.

HEPA filter

Re-install the HEPA filter. Refer to the materials page for replacement filters that meet the H13 filtration standard.

Use thin strips of poster putty and seal the edges above the rim. Stay clear of the white case so that the cover can close flush to the case.

Finish by closing the cover over the HEPA filter.

Secure the hose

The hose comes loose too easily at the base. You can secure it using a retaining ring made from a Velcro cable tie.

---

Simply install the hose, and then cinch the cable tie around the hose, with fuzzy side out.

The hose is now secured.

Attach to the mask

The hose can be attached to any mask as long as there’s enough tension on the strap to hold the weight of the hose. My favorite mask for this setup is the Drager X-plore 1950 M/L with a strap taken from the Envo Mask Pro.

If using a trifold mask: the tube should be mounted on the bottom fold. To demonstrate, here’s the bottom of a 3M Aura 9010+ with a 11 mm hole punched using a leather hole punch.

The Board AirPro comes with a hose connector that might come loose while wearing the mask.

A more secure connection [is available here] (https://a.co/d/iDBuav8) (# 1/2” Thru-Bulk Bulkhead Plastic Hose Barb Fittings Union Adapter Fittings for Aquarium Fuel Gas Liquid Air with washers).

However, this connector requires cutting off the non-threaded end, as shown here:

Once removed, it can be installed by screwing in the included nut.

Attach the harness

While the blower unit is lightweight, it must be secured to the body to prevent kinks in the hose.

We recommend the following method of attachment:

34-59 inch leather purse strap. (To wear around the shoulder.) Half inch elastic band. (To attach the blower unit to the strap.) Purchase links are in the materials page.

The unit with harness:

How it looks when mounted (with leather cover and black hose):

I recommend that the blower unit is mounted with the HEPA filter facing towards the body. This convolutes the pathway for contaminated air to reach the filter, and mixes in cleaner air on its way to the filter, and has minimal impact on air pressure.

Check that it works

Since breathing resistance is close to zero, wearing this setup is indistinguishable from wearing a mask with a hole in it. One way to confirm that the mask is set up correctly is to squeeze the air hose. If you feel your breath build up, then you can be reasonably sure that your setup has a good seal.

Failsafes

If the battery runs out, the blower unit continues to filter air passively. Fit scores resemble the fit score of the mask alone. As the blower speed increases from low to high, the effect of the HEPA unit takes over, but does not follow a linear increase in fit score. Generally, medium speed provides the best balance in filtration efficiency, breathability, and pressure. Again, air pressure is important because this alone can prevent contaminants from entering the mask, irrespective of the rating of the HEPA filter.

At medium speed, the battery should last 8 hours. Halfway through a work day, you may attach a USB power bank via magnetic charger to the blower. The blower can charge while it provides air pressure. This is called pass-through operation, and is an important component to the Broad AirPro’s safety profile.

If attached properly, the hose should support the weight of the blower unit, so that in case it detaches from the harness, you don’t lose filtration. In the event that the hose and blower detach from each other, you can pinch the hose closed, preventing unfiltered air from entering the mask. This buys you time to get to safety.

If the hose detaches from the mask, plug the mask with your thumb and get to safety.

Risks

Since you don’t smell your own breath, you can’t tell if your mask has gotten stale. There’s nothing wrong with staleness, but it’s a proxy for other things: looser strap, limp filtration material, degraded foam padding. In short, a worse fit. You have to remember to replace your mask. After one month of using the same Dräger X-Plore 1950 M/L in this setup, fit scores look good with the blower on, and look bad with the blower off. Set reminders to change the mask every few weeks.

A word on backyard firepits. While it’s tempting to wear this to a backyard gathering, even a brief exposure to smoke-filled air will make the unit smell for weeks, and cut the usable life of the filter short. Consider wearing a passively filtered mask instead.

When to change the filter

Fit scores show that the H13 HEPA filter continues to do its job for at least 1 year with medium usage.

Meltblown filters never stop working. In fact, they get better the more particles they trap. With a clogged filter, however, the blower might lose air pressure, even while filtration efficiency remains nominal.

Replace the filter once it looks gray, develops a smell, or when the air pressure seems weaker.

Conclusion

And there you have it, your very own powered respirator.

1.2.1 - Materials

All prices are approximate in USD.

Main Respirator Unit

Item	Where to buy	Cost	Notes
Broad AirPro Respirator	https://a.co/d/3Gs8jAI	45
AirPro Mask Connector Replacement for Broad Airpro Mask	https://a.co/d/0qVh9mG		No longer available
Gorilla Mounting Putty	https://a.co/d/8aiX2MC	7
Velcro Cable Ties	https://a.co/d/gHCxr2I	4
Magnetic USB Chargers	https://a.co/d/cvWa2Ea	16
Scotch Heavy Duty Shipping Tape	https://a.co/d/gZW5b48	3
Nexcare Blister Prevention Tape	https://a.co/d/80zUTnO	5	3M Nexcare refers to a product line that also includes breathable tape, which is NOT airtight.
1/2” Thru-Bulk Bulkhead Plastic Hose Barb Fittings Union Adapter Fittings for Aquarium Fuel Gas Liquid Air with washers -Pack of 3	https://a.co/d/igNL91c	9	Doubles as a way to extend the hose as well

Harness

Item	Where to buy	Cost	Notes
34-59 inch leather purse strap	https://a.co/d/8bd1zm8		No longer available
Half inch elastic band	https://a.co/d/7Br9AiG	6

Replacement Hepa Filters

The HEPA filter is an important component of filtration. If these directions are followed properly, then the fit score of the blower depends solely on the filtration efficiency of the filter.

In my experience, only Broad Air’s OEM replacement filters consistently score above 500 on fit tests. Other manufacturers make replacement filters for the Broad AirPro, and are to be used at your own risk and discretion. Tested fit scores ranges are posted here.

Item	Where to buy	Fit Score Range	H13 (>99.95%)
BROAD AirPro PM 2.5 HEPA Filter	https://a.co/d/5YPByw0	500 - 10,000	Often
H13 HEPA Filter, Suitable for BROAD AirPro	https://a.co/d/fWqDI7R	100	No
Nispira True HEPA Filter Replacement	AVOID	NA	NA

Masks

The following masks are recommended for their superior fit test scores (across many mask wearers) and availability.

Products from these sellers are personally tested with a PortaCount 8020.

Mask	Where to buy
3M Aura 9210+	https://a.co/d/1AOZtPO
Dräger X-plore 1950 N95	https://a.co/d/4u2c7cP

Optional

Item	Where to buy	Cost	Notes
Leather Hole Punch	https://a.co/d/93SXH5t	13	Use the 11 mm or 13 mm for secure fit
Replacement Headgear Compatible with Envo Respirators	https://a.co/d/9JTsN72	12	For use with Drager X-plore

1.3 -

���������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������������

2 - Organizing

A mess is really just items in transit.

• Organizing a room makes it messier at first because more items are going into transit.

Every item has a home.

• Things can move closer to home without going all the way there.
• It’s comfortable enough for the item to be in the home’s vicinity.
• An item’s home tends to be where it wants to be, and it’s often best not to fight that.
• If you lose an item, the first place you look is a good sign of where that item’s home should be.

Items take the bus to get home

• The “bus” is a box that makes stops where items get off.
• There can be many circulating busses.
• It often makes sense to have an “express bus” which is designated for a distant place with few stops.
• An item that’s not on a bus is a “pedestrian” and it has to walk all the way home. Every item needs a “hand holder” to get home. Hence, very few of them can walk at once, since the hand holder only has two hands. When there are too many pedestrians, traffic comes to a complete halt, and the room stays disorganized.
• An item’s home is very often a container or box with a label on it.

Some items are light enough to go on a “flight.”

• Clothes and trash are examples.
• Just toss the item towards their destination.

When an item doesn’t have a home, it goes into the “Lost and Found.”

• These items can be retrieved later and put in transit once they have a home.

Every item has gravity that attracts related items.

• For example, DVDs enjoy being with other DVDs, as well as game controllers, remote control, etc.
• These will orbit the TV.
• Just like gravity, items drift to their preferred place of orbit.
• An item’s orbit suggests its home.

A mass of disordered items in one place is called a Gemba.

• At a Gemba, items are sorted by their gravity, boarded onto a bus to send home, or moved home.
• Busses are set for departure.
• A Gemba is a temporary transit hub. When leaving a Gemba, busses can go to their next stop.
• A Gemba is closed out when most items have been sorted.

The room is organized once most items are at home and no longer in transit.

• Time to relax.

Supplies

Item	Where to buy	Notes
Banker Boxes	https://a.co/d/1G5VdVU	For bussing and storing bulkier items like clothing.
9 x 6 x 4 inch boxes	https://a.co/d/2W5qjHd	For bussing and storing smaller items. These can be converted to be open-top.
White Acrylic Markers	https://a.co/d/hClAe4y	For clear labeling on a colored Post-It.
Post-Its	Various	For labeling items stored at rest. Items in transit do not go into labeled boxes.

Tips and Tricks

• Generally, boxes with open tops work better for busses.
• Boxes with lids work better for homes, since they can be stacked to save space.
• A bus can be converted into a home by adding a label, and then parking it.

Take Five

To overcome inertia from a large work pile, it can help to use a “Take Five” approach. Instead of processing the load at once, select five items to be processed / loaded on buses / offloaded / sent home.

This makes the work discrete rather than continuous, lowers the threshold for getting things done, and enables processing things out of order.

Knolling

In a disordered state, it can be hard to see items individually and properly assess where they need to go. Knolling is the act of arranging items at 90 degrees, spaced evenly. This can help indicate that an item is at home and at rest, while also revealing items that are out of place. As such, knolling is a method to surface the items that need to be put in transit.

Transportation is a Cost

Organizing isn’t free. Time is the universal cost to create and maintain any state of existence. On a more granular scale, transportation is the cost, because it requires time, physical movement, and physical space for the vessel of transport. In lean manufacturing, unnecessary transportation is considered a fundamental waste. A screw is considered to be in transit until it’s fully driven into the part.

Transportation must be reduced in order to maintain a state of organization.

• Place high-use items out in the open.
• Archive low-use items and at the edges of living space, so that they don’t impede movement and traffic.
• Maximize busses, minimize pedestrians.
• You may downsize, as detailed below.

Downsizing

• The major risk of downsizing is regret.
• Don’t downsize items where the risk is greatest.
• One trick to overcoming a sense of loss is to take a photo of an item before discarding, especially if the item is materially worthless.