[Prev][Next][Index][Thread]
Re: Electroplating (hydrogen sulfide hazard)
X-Envelope-From: James.P.Lux-at-jpl.nasa.gov Wed Aug 26 19:06:06 1998
Tesla List wrote:
>
> >used in plating. The only danger in the process that I'm looking at now
> >is exposure to Hydrogen Sulfide gas. And I intend to take precautions to
> >prevent being exposed to it.
>
> You probably should. It is rather poisonous too. Fortunately, you can
> easily smell it even in minor consentrations. If you're working in a
> closed
> environment you should make sure you don't get used to the
> smell of it. It is funny how you can just smell it a bit all the time
> while
> the consentration is actually going up. Nose gets pretty quickly used
> to that smell.
>
H2S is very troublesome. It is about an order of magnitude more lethal
(in terms of concentration) than HCN (hydrogen cyanide). Fortunately, it
is much more detectible AT FIRST than HCN. The problem is that at
concentrations ABOVE about 300 ppm, you cannot smell H2S. 3 breaths of
600 ppm H2S (which you won't smell) is a typical lethal dose. If you
have even a fairly low concentration of H2S in a room, you could walk
in, smell it, and die. So called "sour gas" in oil fields is a big
problem, as it is in the sewer industry, where they can get a sudden
upwelling of H2S from a manhole. In 1984, something like 10 sewer
workers died (in separate events) from H2S.
Just as an example, to produce a quickly lethal concentration in my
garage (20x20x8 ft=3200 cu ft), it would only take reacting about 150
grams of Iron Sulfide. (that is, a bit less than 2 mols). If you are
talking about using gallons of a plating bath, I'll bet there is more
than a couple of moles of sulfur in it.
Here is some stuff on H2S from a safety web page:
The Occupational Safety and Health Administration (OSHA) permissible
exposure
limit (PEL) for hydrogen sulfide of 10 ppm is set 30 times lower than
the
"immediately dangerous to life and health" level of 300 ppm set by the
National Institute for Occupational Safety and Health (NIOSH). Despite a
low
human odor threshold for the gas in air (<< 1 ppm), hydrogen sulfide is
considered to be an insidious poison because our sense of smell rapidly
fatigues, and therefore, fails to provide a good warning of gas
concentration.
The principal route of exposure to hydrogen sulfide is inhalation. Like
carbon monoxide and the cyanides, hydrogen sulfide is classified as a
chemical
asphyxiant. Exposures to this gas can interfere with cellular
respiration and
cause death if an individual's cells are deprived of oxygen (biochemical
suffocation). At low concentrations (i.e., < 10 ppm), hydrogen sulfide
causes
irritation of the eyes, mucous membranes, and upper respiratory system.
When
exposed to higher concentrations (10-50 ppm), persons tend to experience
mild
eye and upper respiratory irritation, headaches, and dizziness.
Concentrations from about 50-200 ppm can cause severe eye and
respiratory
tract irritation, acute conjunctivitis, lacrimation, and difficulty
breathing,
as well as a sudden loss of consciousness. Prolonged exposures at these
levels may lead to bronchitis, pneumonitis, and migraine headaches. At
higher
levels, hydrogen sulfide can cause a severe loss of motor coordination,
coma,
pulmonary edema, respiratory paralysis, and ultimately death.