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Posted By auntysmash
Our PPE supplier is telling us we need to replace activated carbon filters (used in RPE in our paintshop) after 500 hours (starting the count once the packet is opened, and regardless of usage). Others are saying no, it's 500 hours 'in use' i.e. with an airflow through them, regardless of how long they have been out of the packet for. Who is right? I assume it depends on the amount of vapour absorbed, but in that case, how can you tell when they are nearly saturated? For now we're going to take the safer option, but it's expensive!
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Posted By TonyB
Auntysmash,
That's the million pound question with canister based RPE (or are you talking about some other type?). What's more its not even that simple. It also depends on the background level of vapour, work rate (respiration) of the wear and many other factors. Also, how do you know that Activated Carbon is the best medium to be using?
However, IMO regarding the specific question any timeframes should be taken from opening the pack. The carbon will be absorbing (different) materials from the air, even when not being used and therefore are becoming saturated. However, 500 hrs seem a very long time! Normally, if the RPE is being used to control exposure that would be over WEL's then you would only be expecting them to last for 2 Hrs max! - if the background level was say up to 10% above the WEL. If the levels were much higher you may only get 15 minutes!!!
I suggest you really try and do some calculations/monitoring to ensure your using the correct RPE and can justify its useful lifespan.
TonyB
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Posted By Paul Leadbetter
Stuart
The life of a carbon filter will depend on the circumstances of use (vapour conc, etc) but 500 hours seems a very long time.
If the vapours you are protecting against have a strong smell (and aren't particularly harmful), the cartridges can be changed when the users notice the smell inside the mask. However, this will not work with solvents like n-hexane because of the high odour threshold.
By the way, I hope you are not using negative pressure RPE to protect against isocyanates.
Paul
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Posted By Merv Newman
I too thought that 500 hours was a very long time, but decided to hold back and leave it to others as my experience could well be past it's "best by" date.
However, seems that others are taking the same view. Cartridges received in sealed packages will have a "shelf-life" date on them which could be anything up to five years. Once unsealed they start to deteriorate. The rate of that deterioration will depend, as others have said on background and in-use levels of contaminants (don't forget synergy) and humidity.
It is an extremely complicated subject on which, I think, only the manufacturers will have done any decent research. One hopes.
I have heard of quite a few "rules of thumb" on this one but they all come down to far less than 500 hours.
I was taught (well after WWII) that cartridge face masks could have, in the best of circumstances (well fitted, proper care and feeding) a maximum protection factor of 5. Working in a 100% TLV atmosphere would/could allow 5 days of use. Change every week or 40 hours)
Used or not, unsealed cartridges were marked with a discard date of one month from date of opening.
Also, was taught NOT to rely on sense of smell to detect penetration. Too many substances have detection thresholds much higher than their effect level. And people can get used quite quickly to the most appalling stinks.
If costs are too high then it might be more economical to look into controlling release at source or installing Local Exhaust Ventilation.
Have a nice day
Merv
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