This is an expansion of the Scott C420 Powered Air-Purifying Respirator (PAPR) web page.
Wiki) was issued designed and introduced in 1959 for protection from chemical and biological agents. It was used up till the 1980s.
Canteen 1 QT with NBC M-1 Cap
Filter Element Set, Chemical-Biological Mask M13A2, NSN: 4240-00-165-5026, Contract: DAAA09-85-C-1276, Mine Safety Appliances Co, MSA p/n: 303924
M256A1 chemical detection kit
Mark I NAAK "Nerve Agent Antidote Kit"
convulsive antidote for nerve agents
M-258A1 decontamination kit
2800901 Protective hood, Randolph Monro, US Government, Jul 30, 1957, 128/201.15, 128/201.29, 2/202 -
Filtered then Exhaled air is circulated under hood to greatly improve overall protection. Works with M17 mask.
2821192 Leakproof Gas Mask, Randolph Monro, US Government, Jan 28, 1958, 128/201.15, 128/201.25 - includes hood
2910979 Canisterless gas mask, Brumfield Richard S, Frank Shanty, Secretary of the Army, Nov 3, 1959, 128/201.15, 128/206.12 -
The filter contains: Glass fibers, Organic fibers, ASC whetlerite Charcoal or filters made using patents:
2741246 Gas masks, Litchfield George R, Secretary of the Army, Apr 10, 1956, 128/201.13, 128/206.15 -
2775967 Respirator, Eugene Sovinsky, Secretary of the Army, Jan 1, 1957, 128/206.12, 128/207.11 -
3486730 Quick disconnect coupling and valve combination, Potash Norman, Us Army, Dec 30, 1969, 251/149.7, 285/244, 141/346, 285/148.21, 128/202.27 - for use in aircraft with pressurized feed
3513840 Mask inlet valve cap assembly, Potash Norman, Us Army, May 26, 1970, 128/207.12 - improved design
3635217 Drinking and resuscitation mask, Potash Norman, Us Army, Jan 18, 1972, 128/201.19, 128/202.13 -
These were on eBay late 2017 as New Old Stock.
The Wiki page for GP-5 Gas Mask (Wiki) lists the components:
SHM-62, SHM-62u or SHN-62mu Face Piece,
Anti Fogging Lenses
The hose is mentioned in relation to a tall can type filter that would be carried in the haversack.
Fig 1 Mask
Fig 2 GP-5 Filter
Fig 3 40 mm hose
Fig 4 anti fog lenses
Fig 5 Carry Bag
Fig 9 Spare Lens kit
Fig 10 Spare Lens Kit w/Cyrillic Instructions I can not read.
It's not obvious how to change the lenses.
Similar to the hood that goes with the Scott C420.
This is not a gas mask, but serves a similar purpose so I'm putting it on this web page. The main thing to note is that this particular model (3M 8511) contains an exhalation valve. This makes it comfortable to wear for extended time periods. Masks without that feature are very uncomfortable to wear.
That valve means that if worn by a sick person and they exhale COVID-19 particles there will be some filtering action. I suspect that the amount of virus particles that escape is smaller than what escapes from a home made face mask that has no pretense of of fitting the face. Note the N95 mask contains electrostatic fibers that capture particles (see patent 4215682 below). In photos of president elect Biden you can see he is wearing two masks. Probably an N95 with valve under the cloth home made one.
There is an expiration date. I believe it's related to bio-degradation of the elastic band. When the band gets weak it may break allowing the mask to move away from the user's face making an air leak. Many of the DIY face mask projects were on hold recently (late March early April 2020) because the makers had not yer received the elastic bands they had on order from China.
There are also N95 masks that do not have the anexhalation valve (3M). The problem is that they get wet on the inside because of moisture build-up. That's why the valve was invented.
Official 3M white paper on Decontamination of N95 Filtering Facepiece Respirators.pdf
The only process that's received a EUA is Vaporized Hydrogen Peroxide (VHP). The white paper lists a number of those and 3M test results.
- Ethylene Oxide or formaldehyde because the next user may inhale residue,
- Ionizing Radiation because it degrades filter performance,
- Microwave because of melting the respirator near metal components,
- High Temperatures above 75 deg C (Autoclave or steam) significant filter degradation,
- ethanol, isopropanal, quat solutions, soaps, detergents all of which degrade filter performance.
20020185133 Filtering face mask that has a new exhalation valve, Daniel Japuntich, Vaughn Grannis, Harold Seppala, Anthony Ferguson, 3M, App: 1992-05-29, -
4215682 Melt-blown fibrous electrets, 3M, 1980-08-05, - the filter has electrostatic properties and so attracts particles. This means most methods cleaning methods may degrade the filtering properties if they effect the charge on the fibers. Liquid Hydrogen Peroxide is one of the methods that will remove particles from the fibers and leave their charge.
4681801 Durable melt-blown fibrous sheet material, 3M, 1987-07-21, - adds carbon fibers for chemically protective garment.
3333585 Cold weather face mask, 3M, 1967-08-01, - That's to say that the mask gets hot and moist because of exhaled hot air. Hence the need for the exhalation valve!
3971373 Particle-loaded microfiber sheet product and respirators made therefrom, 3M, 1976-07-27, -
4807619 Resilient shape-retaining fibrous filtration face mask, 3M, 1989-02-28, - see the Maxi-Mask below for a molded mask. Note these are bulky to store.
Rabbit Air Room Filter
I have marginal allergies that show up when there's a lot of pollen so have Rabbit Air brand Minusa2 unit in the bedroom. It has some features that many other room air filters lack.I added this endorsement because of seeing the YouTube by Fran Blanche:
1. There's a light sensor and when in auto mode will slow down the fan at night, i.e. it's very quiet at night.
2. There's a particle filter on the right side and when in auto mode will speed up the fan if it senses particles. This typically happens if you walk by it.
3. It uses a Brushless Direct Current Motor (Wiki: BLDC), and like the Big Ass Fan, it runs 24/7, so that helps reduce the electrical usage.
4. Instead of having one filter that's a pack of four filters that can be customized for specific needs.
The BlueAir Filter Problem -
The box says "Filters out: Dust, Bacteria, Pollen, Latex Free, Protects against frigid winter air. Lawn Mowing, Infant Care, WInter Jogging, House Work, Garden Weeding. WARNING: The Maxi-Mask should not be used for toxic or hazardous air contaminants, such as paint spray, asbestos, silica, cotton or other toxic dusts, gases, fumes and vapors. Replace mask if breathing becomes more difficult from prior usage."
It does not mention any medical applications. There is no valve like on the N95 mask. There is no expiration date since no harm would come if it fell off. UPC: 011822324045
4807619 Resilient shape-retaining fibrous filtration face mask, 3M, 1989-02-28
patent expired in 2006, so these now are generic.
There are many filters available that fit the standard 40mm masks and powered breathing units designed to remove different things. No one filter will remove everything.
The activated charcoal filter (Wiki) "Active charcoal carbon filters are most effective at removing chlorine, sediment, volatile organic compounds (VOCs), taste and odor from water. They are not effective at removing minerals, salts, and dissolved inorganic compounds."
BS EN 14387:2004+A1:2008 Respiratory protective devices. Gas filter(s) and combined filter(s). Requirements, testing, marking
BS: British Standard
EN: European Norm
UK Health and Safety Executive - Appendix 4 European Standards and Markings for Respiratory Protection -
Organic gases and vapor with boiling point greater than 65 deg C
Inorganic gases and vapor, e.g. Chlorine, Hydrogen Sulfide, Hydrogen Cyanide, but not Carbon Monoxide
Sulfur Dioxide, Hydrogen Chloride and other acid gases
Ammonia and organic ammonia derivatives
PRC68, Alphanumeric Index of Web pages, Contact, Products for Sale