NIOSH Evaluates Diesel Exhaust Controls at Fire Stations

NIOSH has released two health hazard evaluation (HHE) reports detailing diesel exhaust exposures and controls in city fire stations. Both stations assessed by NIOSH had apparatus bays housing diesel-powered emergency response vehicles, as well as living quarters and office spaces for firefighters and other personnel. NIOSH staff members visited the stations in 2024 and 2025 to observe work processes and practices; collect area air samples of diesel particulate; measure concentrations of carbon monoxide, carbon dioxide, and particulate; and conduct ventilation assessments. Measurements of diesel exhaust particulates were well below occupational exposure limits at both stations. Still, the reports recommend minimizing exposures to diesel exhaust, a carcinogen that may also worsen asthma, allergies, and other chronic conditions. 

The first report (PDF) describes a fire station with six apparatus bays equipped with ceiling-mounted air filtration units, exhaust fans, and a louvered outdoor air intake. NIOSH recommends only some improvements to this station’s ventilation system, including repairing the exhaust fans, installing source-capture systems to supplement the air cleaners in the bay, closing apparatus bay doors when equipment is running outside, and removing a bird’s nest found in the outdoor air intake. 

The second report (PDF) describes a station with two apparatus bays equipped with four ceiling-mounted tailpipe exhaust hoses, each of which was designed to connect a vehicle tailpipe to a metal exhaust duct leading to a fan that discharged the exhaust outdoors. This local exhaust extraction system was designed to activate automatically from dispatch calls or when exhaust flow triggered sensors in the vehicle tailpipes. NIOSH evaluators identified several issues limiting the system’s effectiveness: one hose was out of service; the hoses did not fit the tailpipe of the station’s fire engine, so exhaust from this vehicle was not captured; the tailpipe sensors did not work consistently; and firefighters attached hoses to the tailpipes of newly returned vehicles while the engines were still running, contributing to diesel exhaust exposures. The report also describes exhaust hoses swinging “violently” after failing to properly disconnect from vehicles, creating a potential injury hazard. 

Evaluators also found that air in this station flowed from the apparatus bays into the living quarters, potentially allowing exhaust into areas where personnel slept, exercised, and worked. NIOSH recommends that station personnel activate the apparatus bays’ general ventilation exhaust system to supplement the local exhaust extraction system until the latter can be repaired. The agency also recommends that the energy recovery ventilator supplying outdoor air to the living quarters be adjusted to create positive pressure in those areas, and that sweeps should be installed on the doors between the apparatus bays and living quarters. 

Both HHE reports may be downloaded from NIOSH’s website.