Material Details

Warning: many of the parts can only be easily purchased in bulk. In bulk, you can get down to the $15/each price.

See note at the end.

------

You will need:

  1. Plastic sheeting

    • (1mil or thicker recommended). Buy it from a Home Depot or Lowe's or hardware store, near their paint drop cloths. 90cm x 68 cm (about 3 feet by 2.3 feet) needed. But you'll probably need to have to buy a big pack since they don't sell small sizes.

    • $3 from Home Depot.

    • $5 shipped from Amazon.

    • You might be able to use a clear bag that is premade. One possible source is bags made from OPP material, like those from clearbags.com. NOTE: These bags are good but noisy (they crinkle a lot).

  2. A clear/transparent viewport.

    • Thin report covers will work. (probably 1mil) Easiest for people to get is a clear-plastic report cover .

      • $16 for 50 pack shipped from Amazon

      • $12 for 50 pack shipped from Walmart.

      • Most office supply stores or Walmart will sell these in smaller packs.

    • Thicker covers (7mil or thicker)

      • $16 for 100 pack from Amazon

      • You probably can't buy singles of these easily. A printing store might have some.

  3. Filters

  4. Fan + Flange + optional rubber band and screws

    • Fan

      • The fan needs to be able to deliver 30L/min at 1.5 cm H20 of flow resistance.

      • The fan we use is the Sunon MF50151VX-B00U-A99 (available from digikey for about $5, but with $5 shipping)


    • Flange (pictured above)

      • The flange is used to connect the fan to the filter.

      • If you have a 3D printer, you can download and print this STL file. This STL file is specifically for this Sunon Fan and make not work for other models or brands.

      • If you don't have a 3D printer, there are three easy alternatives:

        1. Hot glue the filter directly to the fan.

        2. Get a block of wood / laminate flooring and drill out a 30mm hole. The filter will fit inside that hole. Glue the wood to the fan to make sure there are no leaks.

        3. Glue a piece of plastic to the fan and cut out a hole a little less than 30mm. Then, hot glue the filter to the plastic. This is like #1, but easier to remove.

    • Screws (optional)

      • Screws can secure the fan to the flange.

      • Two M4 screws and nuts that are at least 22mm long will help secure the flange to the filter. M3 can also be used.

      • If you don't have screws, zip ties and twist-ties (like at the grocery store, produce section) will work. Gluing also works.

    • Rubber band (optional)

      • A rubber band will help keep the flange attached to the filter.

      • The rubber band needs to be wide (at least 0.5inch) and not long (less than 30mm)

      • Without a rubber band, if you knock the fan hard, it may pop out. If you are gentle, the filter will not fall out.

      • The best rubber band is a "lobster rubber band". 1.25 inch (grey) x 0.5 inch is the one I found. (Only place to buy is from JCS search on ebay. Or Amazon sells the 1 inch version, which works but is tight. Both are packs of 100s.) You might be able to get one from a store that sells seafood.

      • Another good option is to take an old 700C bicycle tire (<30mm) and cut a cross section.

      • A rubber band from broccoli (produce section) will work if you double it up.

      • A normal rubber band twisted over and over won't work that well. The rubber band will still compress, but the goal of the rubber band is to prevent lateral slipping. And doubling up isn't great for that.

      • You can also use tape if the filter pops out.


5. Electronics for 5V to 12V (and any plug adapters)

  • The recommended fan requires 12V power.

  • 5V USB to 12V step up converter

    • One side plugs in to a standard USB port. The other side outputs 12V to a 5.5mm x 2.1mm plug.

    • $7 for a 3 pack from Amazon. These can fail sometimes, so a 3 pack isn't a waste.

  • Plug Adapter 5.5mm x 2.1mm plug (female)

    • ~$10 for a 10 pack on Amazon. This one requires a small eyeglass-size screwdriver. You only need one female plug, but it's hard to buy just female plugs and not to buy kits.

    • You can also use a push connector, but these may pull out more easily.

  • If getting parts is hard for you (for example, outside the US), you can also directly wire any 12V power source to the fan. This includes using a 10-pack fo AA batteries.


6. USB battery pack.

    • A USB battery pack (if you want to use this portably). You can test with a USB wall plug or a USB port from any computer. (uses less than 1Amp, 5W of power)

    • Some USB power packs automatically turn off if the current draw is too low. The Sunon fan typically draws about 400mA of current (about 2Watts). This "cut-off" was observed in just one USB battery pack we tested.

    • We know this battery pack works fine. $21 for a 3pack of 5000mAh battery packs from Amazon. You will want at least a 2 pack so that you have a backup battery.

    • A 5000mAh battery typically lasts at least 5 hours with no problem. They can often last 10 hours. Battery packs, even on Amazon, vary greatly in whether they deliver full capacity.


7. Packing tape

  • Any packing tape should work. You want to make sure the packing tape doesn't rip too easily, but we haven't encountered any packing tapes that tear too easily.

  • Clear packing tape is better for seeing.

  • I use Duck brand tape that is about $12 on Amazon for 4 rolls. It is 1.6mil thick, which works great.

  • You can also buy a single roll of 1.8mil thick from Amazon for $4.

  • Or buy from your local hardware store or box store.


8. Neck strap or equivalent.

  • The neck strap will keep the bag from leaking around the neck.

  • Elastic is good, since it compresses, but stretches. Stretching is needed when you turn your neck or move around.

  • Velcro or rope/cord will work, but doesn't stretch. If tied tight, it may be uncomfortable for breathing. If tied loose, it may not make a good seal.

  • This 1/2 inch elastic is what I use, about $10 from Amazon. You will only need about 2 yards per mask.

    • TIP: wrap it twice or three times around. This gives it a lot of room to stretch. It also doesn't need to be tied tight; you can loop it a few times and it will stay put.

    • TIP: a twist tie will lock the elastic well, as will a toggle lock.

  • For testing and casual use, you can also use a scarf or a neck tie.

    • If there is a neck leak, the positive pressure means it will be your germs that spew unfiltered outward. But the amount is minimal compared to most masks.



NOTE: For Amazon, I do use affiliate links. Any money is used for hosting and materials to give away. Any excess will be donated to charity.

Alternatives to bulk-purchasing and self-assembly

Instead of purchasing in bulk, we can send you a kit with all the materials (except the battery pack). Unfortunately, the kit will be $25 for the materials and $15 for shipping in the USA. You will still need to assemble the kit. Email us to ask about this.

The battery pack cannot be sent easily because it is Lithium Ion. They can be easily purchased from Amazon or any box store.


If assembling stuff is hard for you, you might consider alternative ways to heighten your protection:

  • Double masking. ~$5. One surgical mask on the inside. And one KN95 or equivalent on the outside. This is very good protection; we estimate about 90-95% filter efficiency for ~1 micron sized particles and very few leaks.

  • The Broad AirPro for about $60-$70 from Amazon. Supposedly, the filters are HEPA H13, which means they filter > 99.95% of particles for 0.3 microns. However, I don't know how good the quality control is on those filters. HEPA filters are sometimes also made of fiberglass and may not be intended for blowing air directly at the face. See link on fiberglass.

  • For special cases, we can assemble the unit for you or find a local volunteer who may be able to help you. Again, email us.