Particulate respirators are classified as N, R or P combined with a designation of filter efficiency (95, 99 or 100). Particulate respirators with the "N" designation are not resistant to oil mists within the working environment. Particulate respirators with an "R" designation are resistant to oil mists present in the working environment. Particulate respirators with a "P" designation protect against all particulates. There are also three level of filer efficiency against particles 0.3 micron and larger in size. These designations are 95, 99 or 100. For example, a P100 particulate respirator has an air-purifying element (filter) which captures 99.97 percent of all particles of 0.3 microns and larger.