hydrogen sulphide

Question 1

what are H2S

Answer 1

gas produced by anaerobic bacteria.

- heavier than air and locates close to the ground

Question 2

What are the main sources of H2S

Answer 2

tank of liquid excrements.

- most of the gas accumulate on the surface level of the liquid part

Question 3

when is the highest exposure of H2S

Answer 3

o Clearing, emptying, mixing of tank

o Dangerous to the ppl cleaning it

Question 4

Range of detection by olfactory apparatus

Answer 4

People are able to smell H2s only at the conc of 0.25ppm or higher – foul odour of rotten eggs

Animals have similar threshold of olfactory perceptibility to H2S. But they have limited possibilities to announce it (behavioural changes).

H2S at conc of 200ppm and higher –> paralyses the olfactory apparatus.

Difficult recognition of smell

Question 5

what systems are affected by H2S

Answer 5

mucosa of eyeball, respiratory tract, GI tract

Question 6

effects through respiratory route

Answer 6

 Oedema and inflammation of upper respiratory ways (predominant)
 Secondary, enhanced risk of aspiration pneumonia

Question 7

effects through ingestion route

Answer 7

impaired neurotransmission and functionality of NS, skeletal muscle and heart (very rare)

Question 8

clinical signs of H2S

Answer 8

o Accelerated respiration
–> apnoea fits in between (stop breathing)
o Mucosa – bright red
o Oedema, some salivation, mucolytic efflux from nares
o If animals are not removed from the source of gas, the symptoms progress
o If the poisoning is lethal – the reason of death is always the same, i.e. suffocation due to respiratory centre paralysis

Question 9

toxic effects versus ppm dose

Answer 9

0..1-0.2 Threshold of olfactory perceptibility
3-5 Well smelled odour
10 Non- toxic concentration
50-100 Conjunctiva and airways irritation
150-250 Olfactory apparatus paralysis
300-500 Lung oedema
500-1000 Nervous system stimulation, apnoea
1000-2000 Coma, respiratory center paralysis

Question 10

therapy / prevention

Answer 10

o Pinpoint monitoring of sludge emptying and mixing (liquid phase)
o Sludge storage control during flooding – when the sludge is released in the flood
o Ventilation control
o Animal’s removal from the contaminated rooms
o H2S detectors – installed near the ground
o Special cares – employees