MOst of the people who did this method put the warning labels. I dont think it will be dangerous to anyone if they see the warning labels.There were no cases of any injuries to first responders from the h2s suicide victims.
Only in Japan. I am wondering why the use of method dropped suddenly after 2008 eventhough the information regarding this available on the internet
The cost for the ingredients is relatively cheap, no risk of failure, painless, no need to go to the doctor to get any antiemetics
First responders can get injured or killed, even with warning signs: (see "From the CDC," below)
1.) The chemical reaction produces a lot of heat and water. Steam will form on the inside of windows and can destroy signs or make them hard to read.
2.) H2S is not well understood and the sulfur sinks so that a yellow river of it often drains under the car. It is not possible to seal the underside of a car.
Also, your corpse is HAZMAT (harardous waste) and this will limit options for your last wishes.
Your skin, particularly the area around your mouth and/or nose, will likely turn yellow and/or grey.
You car is totaled and is also HAZMAT.
There is plenty of chance of failure and plenty of risk. It does not always make you pass out on the first breath and your SI may make you open the door. This is, essentially, using a chemical weapon against yourself. An additional risk is the chance of other compounds being formed. If done incorrectly, hydrogen cyanide can form and assure you a horrid, terrible death.
From the CDC:
Results: Five of the nine states participating in NTSIP reported a total of 22 chemical suicide incidents or attempted suicides during 2011-2013. These states reported a total of 43 victims: 15 suicide victims who died, seven people who attempted suicide but survived, eight responders, and four employees working at a coroner's office; the remainder were members of the general public. None of the injured responders reported receiving HazMat technician-level training, and none had documented appropriate personal protective equipment.
Please don't do this. There are plenty of methods that do not place others at this kind of risk.
ETA: The reason it was popular in Japan but not other places is that the chemicals required were easily available in household cleaning products there, hence the name "detergent suicide." Those formulations have since been changed, which largely accounts for the dropoff in deaths. For a while, when this was popular, the ingredients needed to make the "soup" were very tough to get through the large retail and auction sites, much as other chemicals are getting tough to find today.