A Respirator is a device that filters the air to remove harmful substances. When exposed to toxic smoke in the air, or toxic ash and dust during cleanup, using a respirator can prevent you from absorbing Lead, Arsenic, Asbestos, and other materials that may be present in the dust and ash.

It does NOT provide oxygen but it can take harmful air with sufficient oxygen and filter it to make it less harmful. NIOSH defines different types of filtration. Examples include N95, R95, and P100.

The N, R, or P designation refers to whether the filter can remove oil aerosols, N = Non-oil-resistant, R = Oil-Resistant, and P = Oil Proof are the three designations. This is primarily of interest when spraying paint or working with machinery that may make oil mists and is not relevant when dealing with dry ash or smoke. You can use any of these N,R,or P to filter ash and smoke.

The number such as 95 or 99 or 100 refers to the fraction of particles larger than 0.3 microns that is filtered by the *material* the filter is made of. 95 refers to 95% filtration, and 100 refers to 99.97% filtration.

There are three relevant types of respirator.

• Disposable masks, often available at hardware stores, N95 masks are common and can often be purchased in a box of 20.
• Half Facepiece respirators: often worn when spray painting, welding, or working with hazardous materials, these have an elastomeric facepiece and a place where cartridges or pads can attach. The type of filter could be P95, P100, or charcoal filters for organic vapors, acid gases, and other hazards.
• Full Facepiece respirators: these operate like the half facepiece but cover not just the lower portion of the face but cover the eyes and seal around the forehead as well. As a system these seal better and so can provide higher levels of protection, including eye protection. These are usually found only in industrial settings.

Although disposable masks and half facepiece respirators are rated for the same system efficiency, the elastomeric half facepiece respirator is more likely to seal better and provide higher levels of filtration when using P100 filters.

Even a days growth of stubble can reduce the efficiency of a respirator dramatically. A filter pad may be P100 filtering 99.97% of the air that passes through it, but beards can make it so that 50 or 80% of the air you breath is actually leaking through the sides of the mask. You MUST be fully clean shaven when using respirators. Also, both half-facepiece and disposable respirators come in different sizes to allow you to get a proper seal around your face. Without a proper seal you might as well not have a respirator.

When working with hazards, NIOSH requires companies to do fit tests. But the public at large working on recovering their house from a fire will not have access to fit testing. It's important to try to find facepieces that fit your face and do not have ANY gaps or leakage in ideal conditions. When working in a respirator, you ultimately will have leakage around the edges, and so the P100 designator is never going to filter anything like 99.97% of harmful materials. We will be lucky if it filters 99%.