Respiratory Protection in the Warm Zone: A Study

Photos by Vicki Sheppard.


By Alberto Caban-Martinez, Bob Kropa, and Vicki Sheppard

Palm Beach County Fire Rescue (PBCFR), working with the Sylvester Comprehensive Cancer Center at the University of Miami’s Health Systems through the Florida Firefighter Cancer Initiative, conducted research that involved atmospheric monitoring for volatile organic compounds (VOCs), many of which are known to be carcinogenic at fire incidents. Because of the surprising results, PBCFR has implemented a respiratory protection plan using a half-mask cartridge respirator with organic vapor and particulate filters for the warm zone of fires.

The Sylvester Comprehensive Cancer Center is entering its fourth year in the Florida Firefighter Cancer Initiative, which is a state funded research project aimed to review the relationship between firefighters and certain cancers. The Initiative encompasses 13 projects ranging from annual firefighter cancer surveys to gear and dermal sampling.

Dr. Alberto-Martinez Caban was the lead researcher for the atmospheric monitoring at the fire scene project. During a fire incident, firefighters are frequently exposed to various hazardous atmospheric conditions in and around the fire scene. To limit exposure to harmful gases and particulates emitted from the fire, the National Fire Protection Association provides technical guidance, model requirements, and standards for the use self-contained breathing apparatus (SCBA) and other respiratory equipment in the hot zone or an immediately dangerous to life or health atmosphere.

Previously, single-compound detectors such as mobile carbon monoxide (CO) monitors have been used by firefighters, providing beneficial measuring of specific harmful gases. However, they fail to detect other gases, such as VOCs, and therefore may not provide sufficient exposure information. Additionally, mobile CO monitors may provide misleading hazard and safety information to firefighters in the hot and warm zones. As other harmful gases such as hydrogen sulfide became known, the on-scene atmospheric monitoring expanded to detect multiple gases. Currently, atmospheric monitoring of fire incidents has been restricted to acute hazards such as low oxygen, CO, hydrogen cyanide (HCN), hydrogen sulfide, and explosive gases, but they have neglected to identify VOCs that could lead to detrimental long-term effects because of chronic exposures.

Previous studies have demonstrated that there are more than 30 VOCs present in smoke particulates. VOCs are organic compounds that become vapors or gases easily. Examples of volatile organic compounds are gasoline; benzene; formaldehyde; and solvents such as toluene, xylene, and styrene. VOCs have been determined to be harmful and extremely dangerous because they may significantly increase the risks of cancer.

Epidemiologic studies have shown that firefighters have increased incidence of select cancers compared with the general population. The occurrence of site-specific cancers, when compared with the general population, raises concern that certain work-related exposures may be contributing to the disproportionate burden of cancer. Taken together, this growing evidence of site-specific cancer within the workforce—combined with laboratory and real-life fire exposure studies—suggest that operating within the warm zone outside of the fire without proper personal protective equipment (PPE) and a lack of a postfire decontamination process may contribute to a firefighter’s overall exposure to harmful gasses and particulates. Firefighters do a good job of wearing their SCBAs within structure fires, even during overhaul operations. However, in the warm zone or the area extending about 100 feet around a structure fire, where significant amounts of VOCs have been detected, firefighters typically do not wear any respiratory protection.



Within the warm zone, typical activities such as atmospheric monitoring, staging of rapid intervention crews, and even pump panel operations by driver operators are performed; the incident command post may also be within this area of concern. Each of these firefighter activities occurring without SCBAs may increase the risk of exposure to respiratory hazards such as CO; polycyclic aromatic hydrocarbons; and other VOCs found in smoke including formaldehyde, HCN, aldehydes, isocyanates, and nanoparticulates. Failure to identify VOCs, which are known carcinogens, could pose additional health risks.

To better understand the harmful gases and particulates at a fire scene, Dr. Caban and PBCFR Battalion Chief Bob Kropa (who is also a biochemist) scientifically examined the fire scene through atmospheric monitoring. The project used a multigas detector situated within the warm zone of actual fire incidents to document exposures from gas and particulate emissions for those firefighters who did not enter the hot zone but operated within the warm zone only. The multigas detector measured CO, sulfur dioxide, chlorine, HCN, ammonia, nitrogen dioxide, nitric oxide, phosphine, and other VOCs. Ambient gas concentrations in parts per million (ppm) were continuously measured and indicated on a light emitting diode display. Alarm thresholds were set at different values by the type of gas (i.e., VOC 2.5 ppm) based on North American standards. If the threshold value is exceeded, a visual (i.e., a blinking light), an auditory loud alarm, and a vibration sensor were activated.

The danger levels for VOCs that are confirmed carcinogens such as formaldehyde, benzene 1 and 3, butadiene, and benzo[a]pyrene are 1 ppm, 2.5 ppm, 1 ppm, and 0.02 ppm, respectively, all well within the detection range of the multigas unit. Data—up to 60 alarms per incident—were stored internally in the device noting the time, duration, and degree of exposure, and were downloaded to a personal computer and placed in a digital spreadsheet.

At fire incidents, the multigas detector was used by firefighters and investigators to obtain readings as part of a standard operating procedure from specific areas of the fire scene including the warm zone. The research project detected and documented standard and above-standard sustained levels of VOCs within the warm zone of regular fire incidents as well as one live fire training session. Harmful VOCs were present from 10 to 100 feet from the structure in the warm zone, exposing firefighters to cancer causing gasses and particulates. The multigas detector data collected at each fire response indicated sustained levels of VOCs where detected in the warm zone of each of the fire incidents.


Based on the measures collected in each of these cases, it is apparent that firefighters should not only implement the use of multigas detection in the warm zone but also include respiratory protection when in this proximity. The result of this project led PBCFR to implement multigas monitoring at fire incidents and respiratory protection in the warm zone with a half-mask with organic vapor and N100 particulate filter cartridges. The negotiated cost of the masks are minimal: approximately $14, with the organic vapor cartridges costing approximately $18, having the added benefit of N100 particulate protection in addition to the VOC protection. PBCFR has placed a total of 85 four-gas monitors and 16 five-gas monitors in service. A four-gas monitor was placed on every engine, aerial, battalion chief, and special operations vehicle, while a five-gas monitor was placed on every emergency medical services captain vehicle. Also, the fire investigators and Training Division both use four- and five-gas monitors. In addition, PBCFR has issued a half-mask respirator to each firefighter (more than 1,300) and placed three sets of organic filter cartridges per seat in each apparatus.

Policies and procedures were developed that detail the multigas atmospheric monitoring process and use of the half-mask cartridge respirators with organic vapor filters. They may be used when organic vapors are the only abnormal gas present and when oxygen levels are normal (i.e., not in the hot zone or IDLH zone inside of a structure fire). The half-mask cartridge respirators with organic filters are also useful for wildland fires, pump panel operations, and incident safety officer functions. Hands-on training and a training video were produced on the proper use of the masks and filters, emphasizing that the masks are to be used in the warm zone only and not in IDLH conditions; it does not protect against low-oxygen environments and respiratory damage because of high heat.

The combination of multigas detectors at the fire scene combined with respiratory protection such as half-mask cartridge respirators with organic filters will assist in limiting exposure to cancer-causing particulates present in the warm zone.

Access the complete research article HERE.


Alberto Caban-Martinez, DO, PhD, MPH, CPH, is an assistant professor in the Department of Public Health Sciences at the University of Miami’s (UM’s) Miller School of Medicine, deputy director of the Firefighter Cancer Initiative at the UM’s Sylvester Comprehensive Cancer Center, and Co-Principal Investigator of the National Fire Fighter Cancer Cohort Study. 

Bob Kropa is a battalion chief for Palm Beach County (FL) Fire Rescue.

Vicki Sheppard is a division chief (ret.) for Palm Beach County (FL) Fire Rescue.

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