Rank: New forum user 
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Hi All,
I'm currently drafting a COSHH assessment for chlorine tablets that we use to disinfect water systems for buildings. The safety data sheet and EH40 state that the short-term workplace exposure limit for chlorine is 0.5 ppm, however the directions of the product require tablets be added to bring the water up to 60ppm at the tank and 50ppm and the outlet (16x 3.2g tablets per 1000L) for effective treatment. By this logic, this means that the person required to do this is well above the safe exposure level.
Am I missing something here as I feel something is not adding up?
Any help is much appreciated :)
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Rank: Super forum user
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The exposure limit refers only to airborne (inhalation) exposure. There are no exposure limits for skin exposure, so you only need to consider the potential for airborne exposure above the exposure limit whilst the chlorine is in concentrated form. Once it is in the water you should ensure that it is kept at the manufacturer's recommended concentration, as this will be what is needed for it to have the required effect.
If you need more on this PM me.
Chris
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Rank: Super forum user
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No expert but do not get the ppm in air and water mixed up. I think most COSHH WEL are ppm in air except stuff like lead, mercury. I think chlorine is soluble in water and evaporates out slowly.
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Rank: Super forum user
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Chris P is correct.
Also
I think you are unlikely to get chlorine gas released from the water in any significant amount unless the ph drops (which is not likely).
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Rank: Super forum user
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So, when we get a strong smell of chlorine, e.g. swimming pool or a factory disinfected water, the airborne concentration is below 0.5ppm ?
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Rank: Super forum user
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The odour threshold is around 0.02 ppm
At around 0.5 ppm it causes irritation and coughing,
3-6ppm causes stinging and burning to the eyes and throat and bleeding fo the nose can occur (airbourne ppm not liquid remember).
So yes, likely below 0.5ppm
Regardless the odour is more likely to be Chloramine you can smell,
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Rank: Super forum user
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Thanks Descartes.
Not a subject I am familiar with, I had no idea that the smell was Chloramine or 'used chlorine' in the water.
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