Hydrogen Sulfide, or H2S, is 

## 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?
    * http://publiclab.org/notes/warren/9-6-2011/hydrogen-sulfide-detection-fart-detector
  * where can it be detected? by smell range?
  * how long does it take?
  * 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 spot source?
* 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](https://www.google.com/search?gcx=w&ix=c1&sourceid=chrome&ie=UTF-8&q=hydrogen+sulfide+monitor#gcx=w&ix=c1&q=hydrogen+sulfide+monitor&um=1&ie=UTF-8&tbo=u&tbm=shop&source=og&sa=N&hl=en&tab=wf&bav=on.2,or.r_gc.r_pw.&fp=4e466e80d018bd5a&biw=1274&bih=702) - as low as $109 for 10-15ppm levels
* who are the potential users? What should the output data look like? Graphs, logs, lights, images?
* what are the data’s uses/outcomes? Legal? Avoidance? Remediation? Regulation?
* are there alternative means of detecting which are dramatically different/cheaper?
  * silver film tarnishes with exposure to H2S (see attached PDF)

## Background

> 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.

> Detection by Smell
> 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.

> 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](https://www.osha.gov/Publications/hydrogen_sulfide.html))