Do you know the deadly nature of today’s fireground smoke?

• Are you getting the needed practice and training in effective air management?

• Are you working in the hazardous environment and making your time-to-exit decision only after your low-air warning alarm activates?

• Are you relying on “filter breathing” as a reliable method of escaping the close call?

“The smoke tasted like liquid, molten plastic …. It was the worst thing I’d ever experienced in my life ….”

-Lieutenant Chris Yob

Most firefighters know that the modern smoke environment is unforgiving and deadly. Tactics classes across the nation are rarely complete without some mention of the expanding toxicity of smoke and the rapid development of “zero visibility” at working fires. We are aware of the highly flammable nature of carbon monoxide (CO) and its ability to cause rapid asphyxiation. There is the growing understanding that hydrogen cyanide serves as the culprit in many of the fireground deaths currently attributed to CO. This invaluable knowledge can have a dramatic impact while working in the modern fire environment and operating in a safe and effective manner that accounts for the many dangers of smoke that is “The Breath from Hell.”

The question then arises, with all the knowledge that has been gained in the past 10 to 15 years, why do firefighters and fireground supervisors operate as if this poisonous smoke does not pose a threat? Many of these same people have been to the hospital to encourage the veterans struggling with cancers or pulmonary deficiencies. Funerals across the country are sobering reminders that many brothers and sisters, most of whom did not have the information we have today, aggressively fought fire and endured the smoke only to have the long-term effects prove deadly. With all of this as a backdrop, why the continued reluctance to recognize that smoke toxicity at every structure fire demands a change in firefighter behavior to meet this challenge?

(1) Photo by Dennis Leger, Springfield (MA) Fire Department.

Change in behavior includes actions that occur before, during, and after the fire. Enhanced training, the proper use of SCBAs, and safe overhaul are key areas to be addressed. It is our firm opinion, however, that the single most overlooked aspect of dealing with the modern smoke environment is the lack of a comprehensive air management program.

In the early 1990s, some of the first detailed work on the treacherous components of smoke began to surface. Dr. Deborah Wallace, in In the Mouth of the Dragon: Toxic Fires in the Age of Plastics,1 details the true nature of the gases that emanate from plastics.


Most definitions of smoke include some description of particulate matter suspended in varying levels of heated air. Soot (carbon), fibers, dusts, and a host of other materials are added for further detail, and varying colors routinely are present. Fire gases capable of asphyxiation, poisoning, and explosive flammability are increasingly being recognized as significant components of modern smoke. Oils and other such materials contribute an aerosol component to smoke that also can be accompanied by extreme variations in heat.

There is a growing recognition that what we’re seeing and not seeing in the modern smoke environment is exceedingly different from what our predecessors faced. Today’s smoke environment is a vicious beast indeed.

The Past

Even in the immediately dangerous to life and health (IDLH) environments of the past, consisting of smoke products from primarily wood-related combustion [CO, nitrogen dioxide, and polycyclic aromatic hydrocarbons (PAHs)], breathing this smoke represented an enormous risk to the short- and long-term health of firefighters. This is all too evident by the numerous cancers and pulmonary diseases our members endured because of their service in firefighting.

Here are some facts, taken from the Seattle Fire Department SCBA Training Guide2 on the various wood-smoke components listed above and how they will affect you, your lungs, and your life.

Carbon monoxide (CO). This is a colorless and odorless gas responsible for the deaths of hundreds of people each year. Firefighters are among its many victims. Its primary danger is the effect it has on the hemoglobin and its ability to effectively carry oxygen. It combines with hemoglobin 240 times faster than oxygen and can cause respiratory distress, aggravated heart conditions, and death.

Nitrogen dioxide. This is a common component of smoke that also causes respiratory distress and edema.

Polynuclear aromatic hydrocarbons. They are carcinogenic organic compounds that result from the burning of materials that have carbon and hydrogen components. These materials are common; more than 100 known PAHs can be present in smoke.

Formaldehyde. This is the same stuff you dunked your biology projects in, and it can find its way to your lungs. It can cause respiratory distress, headaches, and other neurophysiological dysfunctions.

Acid gases. These gases (hydrochloric acid, sulfuric acid, and nitric acid) can cause any number of problems, including respiratory distress, chemical burns, disorientation, and death.

Phosgene. This poisonous gas was used as a chemical weapon in World War I and is a by-product of burning chlorinated hydrocarbons. Its effects can range from blurred vision to edema and respiratory failure. It is heavier than air and, thus, will be in just the right place for advocates of “sucking the carpet.”

Benzene. This component of cigarette smoke is also found in fires. It is a known carcinogen and can cause respiratory distress and asphyxiation.

Dioxin. This deadly by-product of some electrical equipment comes from burning polychlorinated biphenyls (PCBs), commonly associated with older transformers.

The Present

In the modern firefight, smoke involves the toxic elements created by the burning of numerous synthetics, especially plastics. Also of note are the increased amounts of hazardous chemicals present even in the smallest of structures. According to some research, a “smoke production” level reaching 500 times that of a similar amount of wood smoke has become a deadly cocktail that contributes to hundreds of deaths each year. It is responsible for a wide variety of cancers that are difficult to tabulate but are very real in many lives. The bill for this smoke exposure has not yet come due for the fire service, but it is coming. The tragedy will be compounded exponentially if we do not respond appropriately to the knowledge we have right in front of us.

In his excellent book The Combustibility of Plastics,3 Frank Fire details a few of the many poisons, and their sources, you will encounter in the fire you go to tonight:

• Acetals-aerosol containers, combs, lighters, and pens.

• Acrylics-glues, food packages, and skylights.

• Nylon-various household containers, brushes, sewing thread, and fishing line.

• Polyesters-hair dryers, computers, and kitchen appliances.

• Polypropylene-bottles, diapers, and furniture.

• Polyurethanes-shoes, cushions.

Polyvinyl chloride-carpet, clothes, purses, records, and shower curtains.

• Thermosets-TVs, coatings, toilets, buttons, flooring, and insulation.

And the list goes on and on. Among the nasty stuff you will encounter from these and other plastics are hydrogen cyanide, CO, CO2, formaldehyde, nitrogen oxides, ammonia, phenol, benzene, hydrogen chloride, methane, and a host of other crippling by-products that make the Breath from Hell truly hellish.

The New York Telephone Fire serves as a classic example of the resulting effects of toxic smoke exposure. On February 27, 1975, 699 Fire Department of New York firefighters responded to a fire that would change their lives forever. The 11-story telephone switching center fire would progress to a five-alarm inferno that involved tons of PVC-sheathed wiring and PCB-laced transformers. The firefighters were exposed to extended doses of the toxic smoke as they courageously battled the fire. There were widespread reports of respiratory problems immediately after exposure to the heavy smoke and lingering difficulties that were not immediately reported. Table 1 shows the results of a survey of the firefighter injuries that day.

Fire service instructor Dan Noonan, diagnosed with leukemia at age 52, had this to say to reporter Bob Port of the Daily News: “We’ve explained again and again that all 699 men who fought the phone fire suffered some form of respiratory distress. Virtually every firefighter who responded to the phone fire’s first two alarms has cancer.”4 As we ponder the ominous statistics of the New York Telephone fire, it is critical to recognize that the toxic environment of that fire is now the norm for what can be expected in every fire we extinguish. Your firefighters, if not adequately protected by SCBA and trained in air management, are breathing these same poisons.


Two of the least recognized components of the modern smoke environment are polyvinyl chloride and hydrogen cyanide. The former is present in large quantities at most fires today; the latter is a deadly by-product that is the silent killer of the fireground.

Polyvinyl chloride (PVC) is likely to be found in more abundance in today’s homes than any other product. It is devastating to firefighters no matter where they are in the smoke, as its deadly fumes are emanating from materials at every level of the structure. Its “emissions during fires of benzene, chlorinated dioxins, and debenzofurans, known carcinogens, appears to explain the high frequencies of leukemia, laryngeal and colon cancer, and rare soft tissue cancers found in many firefighters at relatively young ages.” (1, 13) PVC fires will also include the presence of the highly acidic gas hydrogen chloride and other gases that impact respiratory and circulatory health.

Hydrogen cyanide is a colorless, odorless gas that emanates from natural and synthetic sources. Unlike CO, which is commonly known to cause death in firefighters, hydrogen cyanide is relatively unknown but is steadily assuming a more prominent place in the hierarchy of the causes of death at fires. It was the gas of choice for Hitler’s death camps (Zyklon B) and the method the terrorists of the Aum Shynrikio religious cult attempted to use in the attack on the Shinjuku Station in Tokyo (May 5, 1995).

A recent JEMS article5 detailed the results of two significant studies done in Paris, France, and Dallas County, Texas, which detailed the following conclusions by collecting blood samples close to the time of smoke exposure and measuring cyanide in survivors as well as in fatalities. The following results were found in the studies:

1. Cyanide concentrations were directly related to the probability of death.

2. Cyanide poisoning may have predominated over CO poisoning as a cause of death in some fire victims.

3, Cyanide and CO may have potentiated each other’s toxic effects.

4. Elevated cyanide concentrations were pervasive among smoke-inhalation victims.

Of significance for advocates of “sucking the carpet” is the fact that carpet fibers are a large source of hydrogen cyanide gas and those fumes develop long before the carpet catches fire. As temperatures increase, in the initial stages of the fire, plastics begin to give off large quantities of various gases. This is called quantitative decomposition and happens long before the materials actually burst into flame. Deborah Wallace describes it this way: “Unlike traditional materials, the temperature of quantitative decomposition for many plastics is less than half their ignition temperatures. Because of this large temperature difference, there is a long period of time when gas is emitted without the warning presence of flame. Generally, the gases emitted during the decomposition stage of a fire are more toxic than those emitted during actual burning. Thus, in many fires, the decomposition stage is the real killer. It is a killer because of its high toxicity and the long period of time between attainment of quantitative decomposition temperature and ignition temperature.” (1, 9)

She states further: “Although most fire fatality victims have high levels of blood carbon monoxide, evidence shows that carbon monoxide is not the only factor in many fire deaths and that the victims had been incapacitated by the irritating products of decomposition long before their blood carbon monoxide levels became fatal.” (1, 35)

It is reasonable to postulate that the “narcotic” effects of hydrogen cyanide can be blamed for the bizarre and incongruent behavior associated with victims of smoke inhalation. There is further evidence in the cases where victims, including firefighters, resisted and even fought with their rescuers until becoming totally overcome by the smoke. The Southwest Supermarket fire in Phoenix, Arizona, serves as a classic example. The courageous efforts of the rescue teams were thwarted on more than one occasion when Brett Tarver fought with the firefighters trying to take him to safety. Since he was a very big and strong individual, it was only after he had succumbed to the environment that they were able to pull him through the debris and out of the building.

This brings us full circle to the questions we started with: Is the Breath from Hell really an acceptable component of your air management plan? Can you afford to compromise your emergency reserve air by working past your low-air warning alarm’s activation point? Is filter breathing going to be anything but a last resort for you or your crew?


The starting point for protecting your firefighters from the deadly smoke they must battle is to implement a thorough, progressive air management program. Your very survival depends on the air you bring to the fight. Everything else rises and falls on ensuring an adequate air supply and knowing how to manage it effectively as you aggressively fight the fire. This should begin before the crews are sent to an alarm and doesn’t end with extinguishment of the fire. The Rule of Air Management is the cornerstone of your air management efforts. It says: “Know how much air you have, and manage that air so that you leave the hazard area before your low-air warning alarm activates.”6

Firefighters must be trained to know their SCBAs as well as, or better than, any other piece of equipment on the rig. This should include a thorough understanding of how to put it in service, maintenance, and what to do when things go wrong. The time to practice switching over to the emergency bypass should not come in a zero visibility cloud of toxic smoke when the regulator has frozen and the mask is sucked to your face. Actions like bypass operations, gauge reading, and emergency transfills should be practiced to perfection before the REAL emergency hits.

Likewise, we know of no sober reason for a competent firefighter’s entering the hazardous atmosphere without first verifying his air supply. Haz-mat and confined-space operations routinely include preentry air checks because of the possibly incapacitating nature of the environments they enter. As you have just learned, normal operations in structure fires routinely contain elements just as deadly. A thorough READY Check7 before entry will eliminate many of the problems and oversights that are routinely getting firefighters into trouble once committed to the IDLH.

(2, 3) Photos by Mike Gagliano.

Once committed to entry, training in breath-control techniques such as skip breathing and forced slowdown reduce air-use rates and promote improved situational awareness. The company officer can rotate members who are exerting more energy to share the load. At some point, it will be necessary to make the time-to-exit decision. This decision will be based on factors such as distance in the structure, fire/smoke progression, workload, and others detailed in “The Point of No Return,” Fire Engineering, March 2005.8


The critical component is ensuring your firefighters are not being required to work into their emergency reserve. The first 75 percent of the cylinder is there for the job. It should be managed to get as much work done as possible for entry, assigned work, and safe exit. The 25 percent reserve should be used only in the case of emergency for the firefighter or the team. The reserve was never intended for an extra couple of minutes of search, line advancement, or pulling ceilings. The low-air warning alarm tells you that you’re using your emergency air. Systematically using the emergency reserve is one of the deadliest practices in the fire service and should be eliminated from your fireground. This practice virtually guarantees that you and those you supervise will be forced to breathe the toxic soup detailed on these pages. Do your own “close calls” already confirm this?

Once committed to the IDLH, regular checks of the crew’s air status are necessary. Air checks should be engrained into the crew’s training at the individual and team level. Train as if your life depends on it.

The Seattle (WA) Fire Department recently issued new standard operating guidelines that include mandatory notification to the IC when a crew reaches the 50-percent mark on their cylinders. This practice allows the IC some lead time in spooling up replacement resources. Further, any crew that has a low-air warning alarm activation must radio out their status, that they are exiting, and where they plan to exit. When a low-air alarm activates in the hazard area, other firefighters are expecting to hear the radio report from the team with the low-air problem. Failure to hear this radio report indicates to firefighters in the hazard area that a firefighter emergency exists and they should react according to Seattle Fire Department firefighter emergency (Mayday) procedures. The removal of the low-air alarm from the fireground in combination with the increased information flow to the IC is an incredible combination for enhanced safety.

These measures do not directly decrease the deadly nature of the smoke we face. They can, however, dramatically reduce the probability of our members being caught in a position where they will have to pull their face piece and be exposed to the Breath from Hell.


A common fallacy antagonists of the Rule of Air Management and air management programs in general promote is that you can always fall back on “filter breathing” should you get in trouble. This notion is a throwback to the days before SCBAs were the norm and “sucking the carpet” was a matter of survival for aggressive firefighters.

With the introduction of SCBAs came the well-worn tactic of stuffing the low-pressure hose into your bunker coat when your air ran out. This met with mixed results and often was forgotten in the anxious moments between the time the firefighter realized his air was gone and the onset of asphyxiation.

Low-pressure hoses are now being replaced with mask-mounted regulators. Many departments train firefighters to pull their hood over their face piece in an attempt to provide a crude filter when their air is gone. This option may provide some “filtering” of large particles and soot but does nothing to stop the deadly gases mentioned above. Filter breathing is nothing but a last, desperate resort and a clear Mayday situation when the firefighter has failed to manage his air. Last, desperate options do not normally end up with positive results.


It is interesting to note some of the descriptions given by firefighters who were lucky to escape the Breath from Hell. Yob (quoted at the beginning of this article) experienced it firsthand, just before he jumped from a three-story building and barely escaped with his life. As he was desperately fighting the effects of CO (and probably hydrogen cyanide) poisoning from filter breathing, he attempted to place his low-pressure hose out a window of the fire building for a breath of fresh air. The eddying smoke came back around, and he got a full breath, which he described as tasting like “liquid, molten plastic.” He said it was the worst thing he had ever breathed, and he knew he couldn’t stand another breath. In his dazed state, he attempted to jump to what he thought was an adjoining roof, only to fall the three stories.

Another fire in Seattle caused a veteran firefighter to die after the fire was out. Bob Earhardt was found on the second floor of the fire building, where he had been operating alone and was overcome by what was believed to be CO poisoning. When found by firefighters, Earhardt had removed his bunker gear and folded it on the floor. Despite the fact that no fire was present, the probable accumulation of gases like hydrogen cyanide, hydrogen chloride, and CO caused a veteran firefighter to become disoriented and lose control of his actions.

These lessons and thousands like them are stark reminders that we are not playing hero in a Hollywood movie. Every emergency we go to is simply the next one that is trying to kill us. We are trained, ready and willing to do our jobs and serve the citizens of our jurisdictions. But, with that willingness must come the reality that it is also our responsibility to recognize and deal appropriately with the hazards that routinely confront us. The deadly smoke of today’s fireground is certainly one of those hazards.

The only reasonable solution is to exit the IDLH prior to exposure to the Breath from Hell. The simplest and most effective way to aid us in exiting is to follow the Rule of Air Management: Know how much air you have in your SCBA, and manage the amount of air you have so that you leave the hazardous environment before your SCBA low-air warning alarm activates.

By keeping your reserve air strictly for emergencies, you greatly increase your odds of never having to filter breathe or sample the Breath from Hell. The immediate consequences of exposure to the Breath from Hell are disorientation, compromising your team, and requiring other resources to bail you out. The short-term consequences are injury, scarring of the lungs, and reduced respiratory capacity. The long-term consequences are evidenced by the diverse and insidious cancers, along with a host of other health issues that destroy firefighters’ lives and haunt their families. And, of course, there is always the possibility that you will immediately join the long list of fireground deaths that are a direct result of smoke inhalation and asphyxiation.

The conclusions should be obvious and sobering:

• Allowing yourself or anyone else under your supervision to inhale the smoke of the modern fireground is a dereliction of duty.

• Ignoring the need for air management training increases the chances that your members will be involved in “close calls,” “near- misses,” and tragedies.

• Staying in the hazard area until your low-air warning alarm activates makes it virtually certain that your crew will eventually be exposed to the Breath from Hell.

• Using “filter breathing” or “sucking the carpet” as anything other than a last resort is foolish and deadly.

• • •

In the tradition of all warfare, it is imperative to “know thy enemy.” Hopefully, this article has given you some additional familiarity with smoke and its toxic components. It is our sincere hope that you recognize the option of filter breathing for what it is: a last resort. Our continued desire is to highlight different facets of the air-management spectrum and partner with you in a safer approach to aggressive fireground operations.


1. Wallace, Deborah, In the Mouth of the Dragon. Avery Publishing Group, 1990, 9.

2. Seattle Fire Department SCBA Training Guide, 1995, 33-35.

3. Fire, Frank L., Combustibility of Plastics, Fire Engineering Books, 1991.

4. Port, Bob, “Red Star of Death,” New York Daily News, March 14, 2004.

5. Alcorta, Richard, “Smoke Inhalation and Cyanide Poisoning,” JEMS, Summer 2004, 6-15.

6. Phillips, Casey, Steve Bernocco, Phil Jose, and Chris Yob, “Train in the Rule of Air Management,” Fire Engineering, April 2003.

7. Gagliano, Mike, Phil Jose, Steve Phillips, and Steve Bernocco, “READY Checks and the Rule of Air Management,” Fire Engineering, June 2005.

8. Gagliano, Mike, Steve Bernocco, Phil Jose, and Casey Phillips, “The Point of No Return,” Fire Engineering, March 2005.

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