IFSI Research Supplement: Exposure Considerations for Outside and Overhaul Operations

Following is Part 2 of the IFSI research supplement, sponsored by Globe. Download the full PDF of the supplement here.

Also, view the 10 Considerations Related to Cardiovascular & Chemical Exposure Risks supplement via Firehouse’s proprietary digital platform Clarity, which includes additional content and videos, here.

#4. Heat stress during outside vent and overhaul

Heat stress is a well-known risk that results from muscular work in heavy PPE and heat from a fire during firefighting operations.

A commonly held belief is that firefighters working on the inside of a structure will experience the most significant heat strain. However, in these scenarios, the overhaul and outside vent crews had the highest measured maximum core temperatures (peak at 101.4–102 degrees F). On average, core temperatures increased by more than 3 degrees F during overhaul and outside vent activities compared to approximately 2 degrees F during inside work (fire attack and search activities).

Overhaul and outside vent assignments may intuitively be considered to be at lower risk for heat stress because they do not occur in a superheated fire environment. However, strenuous physical work in heavy, insulating firefighting PPE can result in significantly increased core temperatures.

It is important to note that in these scenarios, the time for outside vent work (average of 22 minutes) and overhaul work (average of 11 minutes outside and 17 minutes inside structure) were longer than the times the fire attack and search crews worked inside the structure (11 minutes). This difference in work time is common for a typical room and contents fire.

#5. Hydrogen cyanide exposure to outside vent crews

Hydrogen cyanide (HCN) has long been considered an acute hazard that firefighters may encounter during fire responses. The combustion of common household materials—especially those containing polymers, foams, glues and resins—can produce high levels of HCN. However, few studies have measured the air concentrations of HCN for firefighters responding to residential fires where synthetic materials are likely to be abundant.

We set out to measure the air inside the structure (area air concentrations) and surrounding the individual firefighters (personal air concentrations) for combustion byproducts, including HCN, produced during the controlled residential fires with modern furnishings. Area air measurements were collected from the structure during the active fire and overhaul. Personal air measurements were collected from firefighters assigned to attack, search, overhaul, outside vent and command/pump positions.

Several of the HCN air measurements collected at a height of three feet inside the structure during active fire were well above the immediately dangerous to life and health (IDLH) level of 50 ppm. HCN is lighter than air, so concentrations are expected to be higher toward the ceiling or within the smoke layer.

The interior firefighters generally crawled below the smoke layer, lessening their exposure to HCN. Even so, the majority of the personal air concentrations measured from attack firefighters were well above the NIOSH short-term exposure limit of 4.7 ppm, and maximum levels measured from attack and search firefighters exceeded IDLH (50 ppm).

Personal air concentrations for the outside vent firefighters were, on average, above the NIOSH short-term exposure limit of 4.7 ppm, with a maximum level above IDLH (while working outside!). Firefighters performing horizontal and vertical ventilation are likely to be exposed to rising gases where HCN concentrations could easily exceed IDLH.

These results provide strong evidence that SCBA should be used when conducting ventilation of a structure fire, even when working outside. To not wear SCBA during this assignment may put firefighters at risk of chemical asphyxiation and adverse cardiovascular outcomes.

#6. High concentrations of PAHs & particulate exposure on the fireground

Air samples were collected on the fireground to characterize potential exposures to command/pump personnel not wearing respiratory protection. These samples were located either near the engine or near the truck, depending on the wind direction.

Particulate measurements on the fireground were, on occasion, substantially higher than background levels. In addition, average levels of total polycyclic aromatic hydrocarbons (PAHs) and benzene were above background levels. When the samples were positioned downwind of the apparatus, diesel exhaust contributed to the particulate concentrations. In such situations, particle counts from diesel exhaust were similar to particle counts from the fire smoke plume (>100,000 particles/cm³). Diesel exhaust is a known human carcinogen.

Not surprisingly, we found that fireground concentrations of benzene, total PAHs, and particulate were highest when collected downwind of the structure and when ground-level smoke was heaviest. Particles measured were generally in the respirable or sub-micron size range. Particles in this size range are capable of depositing into the lower respiratory system where clearance mechanisms, such as increased mucous production and coughing, are less effective and lung inflammation can occur. These particles would likely be composed of a variety of toxicants, and at this location in the lungs, systemic absorption is likely, further contributing to firefighters taking in potential carcinogens.

Exposure to particulates can also play a role in triggering a cardiovascular event. Numerous epidemiology studies have shown strong relationships between high levels of fine particulate concentrations in the air and increases in hospital admissions and death rates due to cardiovascular events in the general population.

These results suggest that firefighters should try to establish command and pump location upwind of the structure when feasible. If that cannot be done, and ground-level smoke and/or diesel exhaust is evident, respiratory protection should be worn.

How Do I Best Protect Myself Against Cancer and Cardiovascular Disease?

The answer to each concern is often the same: increase fitness, avoid excess weight, eat fruits and vegetables, participate in regular medical screenings, and avoid unnecessary exposures on the fireground.

"Research has been able to now prove and painfully illustrate that all career and volunteer firefighters are at greater risk for work-related cardiovascular events and cancer diagnosis than the typical civilian. Fortunately, there are many things we can do to reduce our risk, with many being at little expense and others costing a bit more.

The answer is personal accountability. All of us can be leaders and set the example for others to see and emulate. Be physically fit. Don’t use tobacco. Know your family history. Get an actual NFPA 1582 physical from a qualified medical professional and then follow up on the findings. Wash your hands, and shower after every exposure. Keep your gear clean, and work toward attaining more than one set. Be smart with your fireground orders and decisions. Be as aggressive at taking care of yourself and your people as you are in the execution of your fireground duties.

It’s simply unacceptable to have thousands of firefighters gather for a funeral when many of the same people won’t change a single thing after attending it. We have a dangerous job and don’t need to tempt fate. Be the change and do it now for your family, your department, your company and you."

— Matthew Haerter, Battalion Chief, Kenosha, WI, Fire Department