A draft page for collecting and organizing information, questions, and projects related to hydrogen sulfide, also known as H2S.

Hydrogen sulfide is a colorless, flammable, extremely hazardous gas with a “rotten egg” smell. It occurs naturally in crude petroleum and natural gas, and can be produced by the breakdown of organic matter and human/ animal wastes (e.g., sewage). It is heavier than air and can collect in low-lying and enclosed, poorly ventilated areas such as basements, manholes, sewer lines and underground telephone/electrical vaults. (via OSHA.gov)

Framing the problem

• Where is this an issue?
• Who's working on this already?
• What information is missing, if any? How will it change the situation?
• What are they key parameters:
  • What intensities & exposure times are harmful to humans or the environment?
  • Where and how can it be detected? by smell range?
  • How long does it take to detect?
  • How fast does it move/change, or how large an area does it affect?
  • What kind of detection? presence/absence? direction of flow? intensity or locating a spot source?
• What should the output data look like? Graphs, logs, lights, images?
• What are the data’s uses/outcomes? Legal? Avoidance? Remediation? Regulation?

Detecting H2S

Wikipedia's article, which is pretty well cited, shows that:

0.00047 ppm or 0.47 ppb is the odor threshold, the point at which 50% of a human panel can detect the presence of an odor without being able to identify it.

This seems to be well below what's cited as a risk to health, but OSHA warns not to use smell as a means to detect it (OSHA.gov):

Can be smelled at low levels, but with continuous lowlevel exposure or at higher concentrations you lose your ability to smell the gas even though it is still present. At high concentrations – your ability to smell the gas can be lost instantly. DO NOT depend on your sense of smell for indicating the continuing presence of this gas or for warning of hazardous concentrations.

• What equipment is available today, and who has access to it? How much does it cost and what is its sensitivity/latency? How much does it weigh and how does it work (air grab sample, continuous flow, soil sample?)
  • on Google Shopping - as low as $109 for 10-15ppm levels
• Are there alternative means of detecting which are dramatically different/cheaper?
  • silver film tarnishes with exposure to H2S, some sources cite discolored copper coins in someone's pocket as a way to diagnose a high exposure

Health effects

Health effects vary with how long, and at what level, you are exposed. Asthmatics may be at greater risk. Low concentrations – irritation of eyes, nose, throat, or respiratory system; effects can be delayed. Moderate concentrations – more severe eye and respiratory effects, headache, dizziness, nausea, coughing, vomiting and difficulty breathing. High concentrations – shock, convulsions, unable to breathe, coma, death; effects can be extremely rapid (within a few breaths).

(Exposure information from OSHA.gov)

Exposure limits from various sources, from an Airgas Materials Safety Data Sheet:

ACGIH TLV (United States, 3/2016).
 STEL: 5 ppm 15 minutes.
 TWA: 1 ppm 8 hours.
NIOSH REL (United States, 10/2013).
 CEIL: 15 mg/m³ 10 minutes.
 CEIL: 10 ppm 10 minutes.
OSHA PEL 1989 (United States, 3/1989).
 STEL: 21 mg/m³ 15 minutes.
 STEL: 15 ppm 15 minutes.
 TWA: 14 mg/m³ 8 hours.
 TWA: 10 ppm 8 hours.
OSHA PEL Z2 (United States, 2/2013).
 AMP: 50 ppm 10 minutes.
 CEIL: 20 ppm

Note that these show toxicity at levels close to the ability of the wearable electronic monitors (see above) can detect -- 10-15ppm; "STEL" means Short Term Exposure Limit, or an "acceptable average exposure over a short period of time."

Questions

Please ask questions to help us expand this set of resources:

Existing work on Public Lab.org

A range of projects related to H2S have been developed here over the years; we're going to try to organize it better, but for now: