When encountering an unknown material or entering an area where the exposure of the product is unknown, firefighters or first responders should use a NIOSH-certified Chemical, Biological, Radiological, Nuclear (CBRN) Self Contained Breathing Apparatus (SCBA) with a “Level A” protection (CDC, 2107b). Level A protection is recommended and should be used until air monitoring readings can confirm a specific material and concentrations of the substance (CDC,2017b). The following is common terminology for establishing distinct working zones and the appropriate personnel protective equipment.
LEVEL A: (HOT ZONE): Is when the greatest level of absorption and inhalation protection is required. This is the highest level of protection for first responders in danger of exposure to known or undertermined hazardous materials or levels above Immediately Dangerous to Life and Health (IDLH) or greater than the Acute Exposure Guideline Levels-2 (AEGL-2) Irreversible or other serious, long lasting adverse health effects or and impaired ability to escape (CDC, 2017b)
LEVEL B: (HOT ZONE): Should be selected when respiratory protection is a priority concern, and is necessary but a lower level of skin protection may be required.
This is a minimal approach for protection to first responders in danger of exposure to unknown chemical hazards or levels higher than the IDLH or greater than AEGL-2. The difference between these levels is it differs from Level A, because it incorporates a non-encapsulating, splash-protective, chemical-resistant splash suit that provides Level A protection against liquids but it is not airtight (CDC, 2017b).
LEVEL C: (WARM ZONE): Should be selected when the contaminant and concentration of the contaminant are known and the respiratory protection criteria factors for using Air Purifying Respirators (APR) or Powered Air Purifying Respirators (PAPR) are met.
This level is appropriate when decontaminating patient/victims. (CDC, 2017b).
LEVEL D: (COLD ZONE): Should be selected when the contaminant and concentration of the contaminants are known and the concentrations are below the acceptable occupational exposure limit or less than Acute Exposure Guideline Level-1 (AEGL-1) notable discomfort, irritation, or certain asymptomatic non-sensory effects for the stated duration times (CDC, 2017b).