Lessons Learned from Hydrogen Sulfide Incident

By Brian Ward

On December 15, 2009, at approximately 12:30 a.m., fire units were dispatched to the parking lot of a community park where police units were performing a routine drive-through looking for suspicious activities. This proved to be one of those times. As a patrol officer approached a parked vehicle, he noticed a strong and pungent odor coming from the vehicle, which made him cautious. As the officer got closer to the vehicle, he saw handwritten notes on the car windows warning that the doors were not to be opened and that “one breath will kill you.” The words “hydrogen sulfide” were also noted. The officer could also see a patient slumped against the driver’s side door inside the vehicle. The officer decided to ask the fire department to respond to his location for assistance.

After listening to the dispatch, Phil Klein, the lead medic for our company, recognized the chemical name of hydrogen sulfide immediately and asked for the hazardous materials team to respond as well. While reading the text on our mobile data terminals, we quickly realized that this was possibly a suicide attempt using a mixture of common household items. A similar case study was published several months prior in a training bulletin and sent to all department members.


Initial response concerns were for the police officer and other responding units already on scene as well as any downwind occupancies through the woods. After investigation and review of the materials, it was determined that there was no exposure hazard. Our medical unit evaluated the first-arriving police officer; it was determined that he kept enough distance so that he did not inhale a lethal amount of vapors.

We established a hot zone with a 330-foot perimeter using the U.S. DOT Emergency Response Guide (ERG), with the realization that if the spill were large, we would expand the hot zone to 0.3 miles. After arriving on scene, I met with police units and determined that we were approximately 350 to 400 feet from the vehicle. After further discussion, I learned that the chemicals appeared to be confined to the vehicle and that the initial hot zone would suffice until further recon was available.

During this time, unified command was established, since this incident was a crime scene that needed fire department assistance before law enforcement could investigate. In the end, the hazardous materials team, the explosive ordnance disposal unit (EOD), the police department, the fire department, and the medical examiner (ME) were all involved and had some stake in mitigating this incident. The public information officers of the police and fire departments were also involved, as the media began to ask questions concerning the incident.

I relayed my information to the hazmat team as it began to research and conduct its own reconnaissance of the incident. After donning full turnout gear with rubber gloves and self-contained breathing apparatus for respiratory protection and using four-gas meters with a hydrogen sulfide sensor, the hazmat team entered the hot zone. They confirmed that one person inside the vehicle appeared to have succumbed to inhalation of the vapors. They also noted that there were several chemicals, including household cleaning solvents and lime sulfur, inside the vehicle. The chemicals were confined to a cooler in the front seat of the vehicle and had begun to crystallize. The vehicle was also scanned for additional hazards that may have been intended to injure or kill first responders. A backpack was noted in the back seat, but it turned out to present no hazard. In addition, the reconnaissance team detected hydrogen sulfide readings of 5 parts per million (ppm) on the outside of the vehicle around the door frame. The National Institute for Occupational Safety and Health’s recommended exposure limit is 10 ppm for 10 minutes.

Although no other hazards were obvious, command decided to use the EOD robot for precautionary measures. The robot ventilated the vehicle by taking out the rear windows; it also provided a video feed and allowed on-scene personnel to gain a better view inside the vehicle from a safe distance. Because the incident was a crime scene, all footage was recorded in the EOD command vehicle. While the robot was operating inside the vehicle, it removed the book bag from the vehicle and took it to a secure location within the park. Once it was determined that all precautionary measures had been taken, the reconnaissance team reentered the hot zone to secure the chemicals and take a second reading for hydrogen sulfide. It took approximately 10 minutes for the vapors to disperse and a reading of zero ppm to be recorded.

The cooler containing the chemicals was removed, and an absorbent was added to absorb the liquid. This aided in reducing and then eliminating the vapor hazard, the primary hazard to on-scene responders.

After all hazards had been mitigated, the scene was turned over to law enforcement and the ME, who had to observe the body. The hazmat team removed the body from the vehicle, thereby allowing any residual hydrogen sulfide vapors to dissipate. Hydrogen sulfide readings were also taken on the patient before the ME was allowed to retrieve the body.


Emergency responders commonly encounter hydrogen sulfide as a by-product of the decay of organic material. Accidental exposure has occurred in situations involving sewage, liquid manure, natural gas, and animal or vegetable matter storage or processing. Hydrogen sulfide is also found at some industrial facilities, such as wastewater treatment plants, petroleum refineries, pulp and paper manufacturing plants, and facilities producing sulfur or sulfuric acid. It is a colorless, toxic, and flammable gas with a strong odor of rotten eggs at low concentrations. Its odor is not a reliable indicator of its presence; high concentrations or continuous exposure deadens the sense of smell. It can be produced by mixing a sulfur source, such as certain paints and pesticides, with an acid, such as those found in toilet bowl cleaners and disinfectants. The extent of the hazard will depend on the concentration of the reactive sulfur and acid.


At low concentrations, hydrogen sulfide causes eye irritation, sore throat, and cough. At intermediate concentrations, symptoms include shortness of breath, headache, dizziness, nausea, vomiting, and pulmonary edema. At high concentrations, it is potentially fatal. Exposure to concentrations at 800 to 1,000 ppm or greater can result in immediate collapse with loss of breathing, even after a single breath.

The National Fire Protection Association 704 Rating is Red 4: Extremely Flammable; Blue 4: Health Hazard, vapor or liquid; Yellow 0: Reactive, Normally Stable. Its vapor density is 1.19: heavier than air. Its Flammable Limits in Air: 4.3% – 45%. Its Odor Threshold is 0.5 parts per billion. The Threshold Limit Value for the Time-Weighted Average is 10 ppm; the TLV/Short Term Exposure Limit is 15 ppm; the TLV/ Immediately Dangerous to Life and Health is 100 ppm; and the TLV-Ceiling is 20 ppm.


As the first-arriving fire department unit, review all available information to determine the extent of the hazards and potential risks to all public emergency responders. Get the appropriate response units en route early; they can always be turned around. Remember, this is a hazmat scene that requires us to take a step back and observe everything. Don’t rush in!

Training is essential not only in identifying the use of hydrogen sulfide as a newer method of suicide but also concerning the interoperability of responding agencies. We have a great relationship with all responding agencies, and it greatly aided our operation. An additional aspect that aided us was the past multiagency training and knowledge of each other’s capabilities prior to the incident.

Take all precautionary measures available. Even though this individual posted caution signs on the windows, additional hazards could have been present. Potential issues could have included identifying the wrong chemicals, no warning signs or notes, or even improvised explosive devices. Regardless, every incident must have the same results with no first responder injuries or deaths.

Because of staffing and scheduling, virtually all fire departments experience staffing “move-ups.” All firefighters on the first-due engine were “riding up,” including a first-shift rookie being precepted. Training acting officers and relief drivers to a competent level is critical in areas such as situational awareness of the scene and crew, communicating with incoming units, and using a methodical risk-based decision-making process.


Cameo Chemicals. Retrieved December 22, 2009; http://cameochemicals.noaa.gov/chemical/3625.

New York State Office of Homeland Security. Retrieved December 18, 2009; http://srems.com/site/newsFiles/DHS_Note_Hydrogen_Sulfide.pdf.

Department of Human and Health Services. Retrieved December 22, 2009; from http://www.atsdr.cdc.gov/Mhmi/mmg114.html.

BRIAN WARD is a firefighter/acting officer with the Gwinnett County (GA) Fire Department. He is a past training officer and current chairman of the Metro Atlanta Training Officers and is a State of Georgia Advocate for Everyone Goes Home. He has an associate degree in fire science and is pursuing a bachelor’s degree at the University of Cincinnati. He is the founder of FireServiceSLT.com and Georgia Smoke Diver #741.

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