stantial heat upon reaction with the sorbent materials in the cartridge.
Dust, fume, and mist respirators can be used only for protection against particular, or certain classes of, dusts, fumes, and mists as specified by the manufacturer. The useful life of the filter depends on the concentration of contaminant encountered. Such particulate-removing respirators usually trap the particles in a filter composed of fibers; they are not 100% efficient in removing particles. Respirators of this type are generally disposable. Examples are surgical masks and 3M® toxic-dust and nuisance-dust masks. Some masks are NIOSH-approved for more specific purposes such as protection against simple or benign dust and fibrogenic dusts and asbestos.
Particulate-removing respirators afford no protection against gases or vapors and may give the user a false sense of security. They are also subject to the limitations of fit.
Supplied-air respirators supply fresh air to the face piece of the respirator at a pressure high enough to cause a slight buildup relative to atmospheric pressure. As a result, the supplied air flows outward from the mask, and contaminated air from the work environment cannot readily enter the mask. This characteristic renders face-to-face piece fit less important than with other types of respirators. Fit testing is, however, required before selection and use.
Supplied-air respirators are effective protection against a wide range of air contaminants (gases, vapors, and particulates) and can be used where oxygen-deficient atmospheres are present. Where concentrations of air contaminants could be immediately dangerous to life, such respirators can be used provided (1) the protection factor of the respirator is not exceeded and (2) the provisions of OSHA's Respiratory Standard (which indicates the need for a safety harness and an escape system in case of compressor failure) are not violated.
The air supply of this type of respirator must be kept free of contaminants (e.g., by use of oil filters and carbon monoxide absorbers). Most laboratory air is not suitable for use with these units. These units usually require the user to drag lengths of hose connected to the air supply, and they have a limited range.
The self-contained breathing apparatus (SCBA) is the only type of respiratory protective equipment suitable for emergency or rescue work. Untrained personnel should not attempt to use them.
Each area where respirators are used should have written information available that shows the limitations, fitting methods, and inspection and cleaning procedures for each type of respirator available. Personnel who may have occasion to use respirators in their work must be thoroughly trained, before initial use and annually thereafter, in the fit testing, use, limitations, and care of such equipment. Training should include demonstrations and practice in wearing, adjusting, and properly fitting the equipment. OSHA regulations require that a worker be medically certified before beginning work in an area where a respirator must be worn (OSHA Respiratory Standard, 29 CFR 1910.134(b)(10)).
Respirators for routine use should be inspected before each use by the user and periodically by the laboratory supervisor. Self-contained breathing apparatus should be inspected at least once a month and cleaned after each use.
Safety showers should be available in areas where chemicals are handled. They should be used for immediate first aid treatment of chemical splashes and for extinguishing clothing fires. Every laboratory worker should know where the safety showers are located in the work area and should learn how to use them. Safety showers should be tested routinely to ensure that the valve is operable and to remove any debris in the system.
The shower should be capable of drenching the subject immediately and should be large enough to accommodate more than one person if necessary. It should have a quick-opening valve requiring manual closing; a downward-pull delta bar is satisfactory if long enough, but chain pulls are not advisable because they can hit the user and be difficult to grasp in an emergency. It is preferable to have drains under safety showers to reduce the risks associated with the water.
Eyewash fountains should be required in research or instructional laboratories if substances used there present an eye hazard or if unknown hazards may be encountered. An eyewash fountain should provide a soft stream or spray of aerated water for an extended period (15 minutes). These fountains should be located close to the safety showers so that, if necessary, the eyes can be washed while the body is showered.