Chemical asphyxiation by use of hydrogen sulfide gas first gained notice through the media in Japan. In the first half of 2008, over 500 men, women and children took their own lives by mixing commonly available household chemicals. By the first quarter of 2009, these types of incidents crept into the United States. The first cases in the United States appeared in Pasadena, California. By May of 2009, Indiana experienced its first incident of this type, which required decontamination of one law enforcement officer and four firefighters. So, what is this Hydrogen Sulfide and how does it hurt us?
Hydrogen Sulfide (H2S) is generally known as “sewer gas” as we find it where the decomposition of organic material occurs in the absence of oxygen. However, by mixing a few household chemicals (an acid and a sulfur based product), anyone can create hydrogen sulfide. H2S is normally found in a gaseous state, is colorless, and has a sulfur/rotten egg odor. It is moderately acidic, is heavier than water and slightly heavier than air. It is also flammable between 4.0 percent and 44.0 percent concentrations. Its NFPA 704 has a blue 4, red 4, and yellow 0, with nothing in the white. The amount that is immediately dangerous to life and health (IDLH) is 100 parts per million (ppm) or 0.0001 percent concentration in air. Keep in mind that the air we breathe has 209,000 parts per million of Oxygen (20.9 percent) and 780,000 parts per million of Nitrogen (78.0 percent). This means the amount of H2S necessary to hurt us is very low.
The primary route of exposure is inhalation as skin absorption is less effective for distribution systemically. However, skin absorption can occur as will be noted later. Once inhaled at high concentrations, H2S causes an inhibition of the cytochrome oxidase enzyme system resulting in oxygen deficiency in the cells. Anaerobic metabolism then occurs which leads to a buildup of lactic acid. This causes an acid-base imbalance. This affects the nervous system and cardiac tissues and death typically results from respiratory arrest. H2S can cause immediate loss of consciousness, coma, respiratory paralysis, seizures, and death. Bronchial and lung hemorrhages can occur which will lead to pulmonary edema. Insufficient cardiac output, irregular heartbeats, and conduction abnormalities may also occur in the cardiovascular system. Renal failure may occur along with nausea and vomiting. Burning and itching of the skin, eye irritation and cloudiness of the eye surface along with blurred vision, sensitivity to light, and spasmodic blinking or involuntary closing of the eyelid.
Tests have revealed that as we move upward from the IDLH concentration of 100 ppm, we find disturbing results. The Lethal Concentration 50 percent kill (LC50) is 800 ppm where tests have revealed that three breaths can kill the average human. At concentrations over 1000 ppm, we find that one single breath can kill the average human. Tests also reveal that vehicles are accumulating 5000 to 6000 ppm during one of these incidents. The level is driven by the purity of the products used as well as the make and model of the vehicle. Generally, higher end vehicles (Lexus, Infiniti, BMW, etc.) are designed to be more airtight as their interiors are quieter than other vehicles, which will allow for a greater accumulation of H2S.
There are a few clues that may alert you that this may be a chemical suicide incident. Let’s assume that we are responding to the report of an unresponsive person inside a vehicle. First, is there any sulfur, chemical, or unusual smells emitting from the vehicle? Next, are there any warning posters on the vehicle? Roughly 85 percent of persons who commit chemical suicide leave a warning poster on the windows of the vehicle. These may read, “DANGER – Toxic Gas,” “Toxic Gas: Hydrogen Sulfide. Stay Away. HAZMAT Team Needed. Keep Distance,” or “Please leave the area immediately and call police and fire. Sorry for the inconvenience. Thank you for your assistance.” Keep in mind that 15 percent of these incidents will not have posters or signs present on the vehicle. Next, look for chemical containers or buckets inside the vehicle. This may be difficult to accomplish if you arrive at the incident during nighttime hours and the vehicle has tinted windows. Some reports indicate that persons are breaking the vehicles inside door handles to prevent their escape should they change their minds. Do not open the vehicle doors or break the windows. Given the high toxicity of this gas in the confined space of a vehicle, the likelihood of having a viable patient when you arrive is virtually zero. Ensure your dispatch center is asking the above questions of the 9-1-1 callers. Also be sure that your law enforcement folks are aware of the dangers associated with this type of incident. The unresponsive patient could easily be misinterpreted as an intoxicated driver. If a law enforcement officer does not receive a response from the patient, they may try to open the doors or break the window. Both of these could result in the DEATH of the officer.
Our response should be similar to any hazardous materials incident. The initial isolation perimeter should be 1,300 feet or roughly one-quarter of a mile. Remember that H2S is flammable so ensure that there are no ignition sources around the vehicle. Level A personal protective equipment is recommended, but Level B is acceptable as the risk of skin absorption (and systemic distribution) is minimal. Once the victim is removed, their clothing should be removed and double bagged. Remember, this is also a crime scene so evidence preservation is also a primary concern. The victim should be decontaminated for three to five minutes. Unfortunately, there have been a few reports that a heavily contaminated patient can continue to off-gas H2S six to eight hours after decontamination “at noticeable levels.” One incident even had a victim that was transported to the morgue, placed in the refrigerator, and began to off-gas H2S when removed the next day. Although this is unusual, it should be a consideration for coroner’s office and morgue personnel and something of which they should be made aware.
If an incident of this type occurs inside a building, an evacuation of the building will likely be necessary. If a vehicle is involved, there are concerns about the contamination of the vehicle. The State of New York requires that any vehicle involved in an incident of this type be destroyed in order to prevent cross contamination. In the absence of this, we must consider what is likely to be considerable contamination of the vehicle’s interior, particularly the fabrics. If a building is involved, it too may have a room, apartment, or floor that is heavily contaminated. The Incident Commander should coordinate with other local officials to prevent cross contamination. The question on how to deal with this particular issue is similar to the discovery of an illicit drug-manufacturing laboratory in a building and does not have a clear, definitive answer as it may vary from one locality to another. Keep in mind that most insurance companies will not reimburse responders for consumables due to the presence of criminal activity. Committing suicide in most states is a felony. This may result in a rapid passing of the reimbursement “hot potato” by insurance companies and vehicle/building owners in an effort to avoid financial liability.
There are a myriad of issues to consider regarding this type of incident. So what do we take away from this? First, ensure that your dispatchers, 9-1-1 call-takers, and law enforcement officers are aware of this hazard. The only thing worse than running one of these calls with a deceased patient in the vehicle would be running one of these calls with a deceased patient in the vehicle and a deceased law enforcement officer outside of the vehicle due to the vehicle’s window being broken or the door opened. We should all take steps now by getting the information out to prevent collateral damage should an incident type such as this occur in our jurisdictions. As in all HAZMAT incidents, slow down. We will very likely not be able to change the outcome of this type of incident, so we must insure that we are all properly protected.