Beyond the Rule of Thumb
Survival Tip 35
by Steven De Lisi
In the November 2008 issue of Fire Engineering magazine, several readers responded to the following question presented in the Roundtable column, page 34: “After salvage and overhaul are completed [at a fire scene], do you conduct atmospheric monitoring before allowing property owners, fire investigators, and others to enter a structure? What gases do you monitor? What levels does your department consider permissible for entry without SCBA?”
Most respondents indicated that their departments make some effort to measure the types and levels of various contaminants, most often carbon monoxide, as well as oxygen concentrations. Of interest was that although the minimum acceptable oxygen levels ranged from 19 to 20 percent (the Occupational Safety and Health Administration (OSHA) Respiratory Protection Standard, 29 CFR 1910.134, defines an oxygen-deficient atmosphere as one with an oxygen content below 19.5 percent), the acceptable maximum concentration of carbon monoxide ranged from 9 ppm to 50 ppm. Although the National Institute for Occupational Safety and Health (NIOSH) considers 35 ppm of carbon monoxide to be the recommended exposure limit as a time-weighted average during a 10-hour workday, one respondent indicated that his department uses the 50 ppm limit, “since firefighting and property loss-control activities don’t last that long.”
Additional gases monitored included hydrogen sulfide and combustible gases. The combination of these two along with carbon monoxide and oxygen seem to indicate that most departments rely on four-gas atmospheric monitors to determine when the interior atmosphere following a structure fire is safe to breathe. However, as we all know, there are many more potential toxic gases-as well as dusts, mists, and particles-that can be released into the atmosphere during a structure fire. Furthermore, during the free-burning phase of a fire, the combustion process is more complete, and superheated air currents can carry contaminants away. In comparison, during the salvage and overhaul phase, smoldering remains produce high levels of toxic materials, because of the relatively cooler interior temperatures that allow a less complete combustion process and less air circulation.
Notably, some departments attempt to measure the concentration of hydrogen cyanide (or hydrocyanic acid); those that do use the NIOSH recommended exposure limit of 4.7 ppm. However, in contrast to the recommended carbon monoxide exposure limit of 35 ppm (which is based on a time-weighted average concentration during 10-hour workday), the 4.7 ppm hydrogen cyanide exposure limit is the maximum concentration allowed during no more than a 15-minute period. Remember that most salvage and overhaul operations will require more than 15 minutes to complete.
Is a structure fire ever considered a hazardous materials incident? For most departments, the answer is no, unless the building is known to store or use large quantities of chemicals. Yet, the mixture of even small amounts of chemicals, such as those found in the garage or utility room of most residential occupancies, should give cause for concern. The same holds true for the vast amount of synthetic components found in modern building materials and furnishings. Never forget that a myriad of chemicals are used in these items’ manufacture; as such, dangerous chemicals, whether carbon monoxide, hydrogen cyanide, or others, will likely be released when these items are involved in a fire.
Would a hazardous materials team, responding to a container leaking an unknown substance inside a box truck or a building, bet its life when deciding whether to wear SCBA, using nothing more than a four-gas atmospheric monitor? Probably not. Instead they would spend considerable time attempting to identify the material prior to making entry. Use of SCBA would almost be a given.
Yet during salvage and overhaul operations, firefighters similarly face an environment that contains potentially dangerous chemicals in unknown concentrations; using nothing more than a four-gas atmospheric monitor can provide a false sense of security when deciding whether the scene is safe, if only the oxygen and carbon monoxide levels are within acceptable levels. There can be plenty more bad stuff in there that will kill you. Never forget that although it may not kill you today, it just may do so tomorrow-or the day after you retire.
Many respondents indicated that prompt and thorough structure ventilation is essential to reducing the contaminant levels and ensuring adequate oxygen levels. Yet despite these efforts, there is still no way to accurately determine just when ventilation has eliminated all contaminants or reduced their concentrations to acceptable levels.
OSHA 29 CFR OSHA 1910.134, paragraph (d)(1)(iii), states as follows:
“The employer shall identify and evaluate the respiratory hazard(s) in the workplace; this evaluation shall include a reasonable estimate of employee exposures to respiratory hazard(s) and an identification of the contaminant’s chemical state and physical form. Where the employer cannot identify or reasonably estimate the employee exposure, the employer shall consider the atmosphere to be Immediately Dangerous to Life and Health (IDLH).”
In this same standard, an IDLH atmosphere is defined as one that “poses an immediate threat to life, would cause irreversible adverse health effects, or would impair an individual’s ability to escape from a dangerous atmosphere.”
Based on our knowledge of the potential range of unknown products of combustion during a structure fire and the fact that firefighters have limited means to “identify and evaluate the respiratory hazards in the workplace” (e.g. use of a four-gas atmospheric monitor), it could perhaps be argued that all phases of a structure fire have the potential to produce an IDLH atmosphere. If that is the case, then the only remedy allowed by OSHA is an atmosphere-supplying respirator, meaning “a respirator that supplies the respirator user with breathing air from a source independent of the ambient atmosphere, and includes supplied-air respirators (SARs) and self-contained breathing apparatus (SCBA) units” as found in 29 CFR 1910.134(b) & (d)(2)(i). This would appear to negate the use of filter masks, which only limit exposure to dusts and particles, as well as air purifying respirators, since neither provides “breathing air from a source independent of the ambient atmosphere.”
From a practical standpoint, is using SCBA during overhaul difficult? Of course-in addition to the added weight, limited mobility, and decreased visibility, there is always the problem of running out of air at the scene. Not all departments are fortunate enough to have air supply vehicles that can respond, thus there is potentially a finite limit to the number of air cylinders available. However, are these reasons enough to forego the health and safety of personnel? If so, consider whether a hazardous materials team would operate without air cylinders during an incident involving the release of an unknown chemical. Most likely they would not. Instead, they would attempt to find additional air cylinders, even if it meant a mutual-aid response. Why should a smoldering structure fire be considered anything less?
One respondent indicated that his department policy is “all mask-all the time,” and that air monitoring of a structure fire during salvage and overhaul was rarely necessary because “we do not enter any atmosphere that contains smoke without the use of an SCBA.” Another stated that some firefighters in his department would resist the use of SCBA during salvage and overhaul, justifying their position with claims such as, “We’ve gone without this for years; why do we need it now?”
For departments that decide to require SCBA use during all phases of salvage and overhaul operations, encouraging personnel to abide by this ruling will likely need more than just words on paper. It will instead require a shift in the department’s culture, where good behavior is rewarded and bad behavior is punished swiftly. However, once a firefighter sees a company officer or a battalion chief inside a building during overhaul without his SCBA, enforcement efforts become difficult, if not impossible. Everybody must play by the rules and know that violations of SCBA policies will be dealt with swiftly.
The one most noteworthy response to this Roundtable question was from a firefighter who stated quite succinctly that “firefighters who use their SCBAs live to enjoy their pensions.” As someone who has attended funeral services for way too many co-workers who died way too soon before retirement from heart disease, cancer, and other job-related illnesses, I couldn’t agree more.
Click here for more info on Steven De Lisi’s book, Hazardous Materials Incidents: Surviving the Initial Response.
Steven M. De Lisi retired after a fire service career spanning 27 years that included serving as a regional training manager for the Virginia Department of Fire Programs (VDFP) and, most recently, as the deputy chief for the Virginia Air Guard Fire Rescue. De Lisi is a hazardous materials specialist and as an adjunct instructor for VDFP. He continues to conduct hazardous materials awareness and operations-level training programs for fire suppression and EMS personnel. De Lisi began his career in hazardous materials response in 1982 as a member of the hazmat team with the Newport News (VA) Fire Department. Since then, he has also served as a hazardous materials officer for the Virginia Department of Emergency Management; in that capacity, he provided on-scene assistance to first responders involved with hazardous materials incidents in an area that included more than 20 local jurisdictions.
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Subjects: Hazmat incidents, off-gassing in structure fires, overhaul, salvage, SCBA use, air management
