When I was young (nearly sixty years ago), my "chemistry set" taught me how to heat sulfur and candle wax to stink up the house.  It had no warning that hydrogen sulfide is toxic and explosive in large quantities.  Is that because people weren't as litigious back then, or because producing large quantities is hard to do?

The reason I ask is that near here, we had a major issue with hydrogen sulfide coming out of an SUV and affecting three first responders who tried to rescue the driver (deceased).  It was announced as a suicide, but I thought if a fellow wanted to end it all, that doesn’t seem like an easy way to do it.

And there is at least one known case of deaths in an SUV from hydrogen sulfide.  I’ve read a few other reports of problems from people leaving the vent hose off of a battery in the passenger area of a car.  Maybe this week's incident was not a suicide.  (Maybe putting a lead-acid battery inside a passenger compartment is a really stupid thing to do.)

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    $\begingroup$ Sadly, there are quite a few cases like you mention in the first sentence of your third paragraph and the less said about the whole thing, the better. Hydrogen sulfide has the unfortunate property of being extremely easy to detect by smell, until, shortly later, it cannot be smelled at all. $\endgroup$
    – Ed V
    Dec 22, 2021 at 19:37
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    $\begingroup$ Toxic as it is, H2S is much more smelly than it is toxic. The idea was that the smell will compel you to stop heating before you have a dangerous concentration around. Also, a small amount of sulfur in a beaker won't produce much H2S in any case. Also, a house is a lot bigger than a car. So no, I don't think it presented a serious danger. $\endgroup$ Dec 22, 2021 at 20:12
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    $\begingroup$ As @EdV states, the nose becomes accustomed to H2S -- see how H2S can cause anosmia: pubmed.ncbi.nlm.nih.gov/10805151 . Though the first whiff can serve as a warning, our olfactory sense is not good at measuring the amount. However, the tiny bit of gas made from paraffin and a sprinkle of sulfur is harmless -- a bigger danger is igniting the furniture with a candle. $\endgroup$ Dec 22, 2021 at 23:31
  • $\begingroup$ oh those old Chemistry sets were amazing and wondrous things, then came the personal injury lawyers (and probably some serious personal injuries) $\endgroup$
    – uhoh
    Dec 24, 2021 at 23:08

2 Answers 2


The problem with H2S is that it is both highly toxic (albeit not quite at the level of HCN but surprisingly to me, too close) and with uncommon properties such as at a threshold of exposure, a suppression of the ability to detect any smell.

The latter is particularly pernicious as one can, apparently, achieve a toxic dose while not even realizing that one is continued to be exposed to the extent of having actually received a fatal dose (reputedly, a 10 minute exposure at 50-100 ppm destroys the sense of smell and thus results in the loss of ability to sense its presence through smell). Also, pathways of fatal ingestion also relate to a limited extent to skin contact, albeit sewer workers wearing a gas mask with extended exposure could, for example, actually fall victim to this deadly poisonous gas.

The victims with fatal doses have actually been referred to as "the walking dead" as they will, progressively sicken over a course of hours, suffering irreversible organ damage leading to death.

I agree that general knowledge and labeling on H2S is deficient, and that there is an issue, as you noted: "It had no warning that hydrogen sulfide is toxic and explosive in large quantities".

I also view this a failing relating to the quality and availability of knowledge in the field of inorganic chemistry. In the case of poisoning in a car with a battery, this knowledge base apparently extends to electrochemistry as well.

As such poisoning from H2S is, in certain locales (Japan being an exception), in my opinion, can be more likely be the result of absence of knowledge and proper labeling than intentional suicide.

Some confirming references include to quote:

Hydrogen sulfide is a highly toxic gas—second only to carbon monoxide as a cause of inhalational deaths. Its mechanism of toxicity is only partially known and no specific therapy exists for sulfide poisoning....No antidote is currently available for sulfide poisoning and treatment is largely supportive.

Per the CDC, to quote:

Hydrogen sulfide is well absorbed through the lungs; cutaneous absorption is minimal. Exposure by any route can cause systemic effects...However, although its strong odor is readily identified, olfactory fatigue occurs at high concentrations and at continuous low concentrations. For this reason, odor is not a reliable indicator of hydrogen sulfide's presence and may not provide adequate warning of hazardous concentrations...Inhalation of high concentrations of hydrogen sulfide can produce extremely rapid unconsciousness and death.

  • $\begingroup$ I appreciate all this info, and suspect the authorities were too hasty in calling the event a suicide. However, that wasn't exactly my question ()in bold in the OP and in the title). But I did learn a bit more here, so I appreciate it. $\endgroup$
    – WGroleau
    Dec 25, 2021 at 7:11

I doubt the article is accurate. Hydrogen sulfide is noticeable at less than 1 ppm and up to 100 ppm causes only sinus irritation in a half hour exposure. It is very dangerous as 150 ppm can cause loss of smell sense in minutes. H2S is common in oil/ gas production so oil companies and governments have extensive rules concerning it. In particular it causes stress corrosion cracking of high strength steels so NACE MR 01-75, now ISO 15656 has detailed rules for H2S. Internal combustion engines do not produce it in quantity. I would like to see some technical analysis of how a lead acid battery can produce H2S in quantity. Also prior to 1940 , it was not unusual for an auto battery to be located under the floor of a car. I have seen a later model Cadillac with the battery under the back seat so apparently that is not a unique location. I have never seen another report blaming battery location for mysterious deaths. I got some information from SPE Sour Gas Design Monograph , 1993 ; I doubt it is readily available. Pardon my ramble but I like H2S it provided me a large portion of my career. PS ; From what I find on the net , in the US sulfur is limited to 15 ppm in gasoline, there are exceptions for off-road and other categories.

  • $\begingroup$ Sorry, some research and experience with H2S (and lack of knowledge in the general population) a critical aspect, which I have experienced (that is with a total suppression after some level of exposure to continue to smell the gas at all) is common. Even more problematic, this can result in achieving a fatal dosing and not immediately realizing that you have received a fatal dose. Actually referred to victims as the "walking dead" as a irreversible successive occurrence of organ failure resulting in death over time. $\endgroup$
    – AJKOER
    Dec 25, 2021 at 3:29

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