The following general considerations apply to instrumentation which might be used in potentially explosive atmospheres or in atmospheres which may contain highly toxic airborne chemicals. A and noted below) and/or carcinogenic chemicals that may have contaminated surfaces or may be found in airborne concentrations.  

Instruments shall not be used in atmospheres where the potential for explosion exists (see 29 CFR 1910.307) unless the instrument is listed by a Nationally Recognized Testing Laboratory (see 29 CFR 1910.7) for use in the type of atmosphere present. Check the class and division ratings prior to use. When batteries are being replaced, use only the type of battery specified on the safety approval label. Do not assume that an instrument is intrinsically safe. If uncertain, verify by contacting the instrument's manufacturer or contact our Technical Center.

For atmospheres containing carcinogens or highly toxic chemicals, a plastic bag should be used to cover equipment to limit contamination. Ensure that the plastic bag is not tightly sealed as this can cause back pressure on the pump. Properly decontaminate all equipment to minimize potential contamination of persons or objects when sampling is complete. To the extent possible, gross decontamination should be performed after use on-site.

Direct–reading instruments (sometimes termed real-time instruments) provide information at the time of sampling, thus enabling rapid decision-making. These instruments can often provide the trained and experienced user the capability to determine if site personnel are exposed to concentrations which exceed instantaneous (ceiling or peak) exposure limits for specific hazardous materials. Direct-reading monitors can be useful in identifying oxygen-deficient or oxygen-enriched atmospheres, immediately dangerous to life or health (IDLH) conditions, elevated levels of airborne contaminants, flammable atmospheres, and radioactive hazards. Periodic monitoring of airborne levels with a real-time monitor is often critical, especially before and during new work activities. Data obtained from direct-reading monitors can be used to evaluate existing health and/or safety programs and to assure proper selection of personnel protective equipment (PPE), engineering controls and work practices.

A chemical that has a median lethal dose (LD50) of 50 milligrams or less per kilogram of body weight when administered orally to albino rats weighing between 200 and 300 grams each.

A chemical that has a median lethal dose (LD50) of 200 milligrams or less per kilogram of body weight when administered by continuous contact for 24 hours (or less if death occurs within 24 hours) with the bare skin of albino rabbits weighing between two and three kilograms each

A chemical that has a median lethal concentration (LC50) in air of 200 parts per million (ppm) by volume or less of gas or vapor, or 2 milligrams per liter or less of mist, fume, or dust, when administered by continuous inhalation for one hour (or less if death occurs within one hour) to albino rats weighing between 200 and 300 grams each