There are several factors which affect how long the mask with adequately
filter out vapours. The previous posts are all correct - once opened, a
filter has a finite life, even if you don't breath through them. The length
of time that a filter will work while you're using it will also be affected
by the vapour concentration, the chemical itself and your work of breathing
- if you're just standing around there is not as much air moving through the
filter than if you're working hard (breathing heavier and faster) and
therefore the filter will last longer.
The other important points are: they only filter our the contaminant. If
the contaminant has displaced oxygen to the point that the oxygen levels
have gone below safe limits, then you need to switch to a supplied (fresh)
air system. Not usually a problem in a home workshop, but in a cellar or
pit this can (and has) become a fatal consequence.
Not all filters are created equal. For wood dust issues, a particulate
filter should be fine, and if you use one with a carbon filter, it may block
up really quickly. Some chemicals attack carbon filters (and the exposure
limits are measured in minutes) whereas other don't and the exposure limits
can be measured in days (or weeks) You should really consult the experts
for an idea of the best filters to use.... Again, for most of what happens
in a home workshop, general particulate filters with a carbon filter are
usually adequate.
You need to ensure that there is a good seal around the mask - here in
OZ, in the workplace, the Australian Standard requires all persons who wear
respiratory protection not have facial hair outside the nose/mouth borders
(the so-called oro-nasal cup) i.e.. small goatees are fine, along with
Hilter style moes, but handlebar moustaches and full beards are not.
HTH, (and the usual disclaimers)
Trev
On Sun, Jan 16, 2011 at 1:26 AM, Jim Miller <jim@...> wrote:
>
>
> Safety masks are inexpensive and are available at HD and Lowes. They're
> good
> for dust and vapors. They have replaceable filtration elements.
>
> Recommended.
>
> jim ab3cv
>
> [Non-text portions of this message have been removed]
>
>
>
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