On Sun, 13 Jun 2010 11:15:38 +0100, Fred wrote:

Thanks. I guess I just need to slacken mine a little so that it
doesn't press so hard.

Just needs to hold the bottom of the mask against your chin to seal,
no need to be tight.

I did consider a mask with replaceable filters but Arco was the only
seller I had heard of and I was nervous about buying from an unknown
company.

Arco are hardly "unknown" they are big supplier of PPE to industry
for a long time (est.1884) with warehouses/trade counters in many
places.I think there has been a bit of move to more "retail" selling
in recent years.

I think the sites I found (via google) were selling boxes of thirty
filters,

That is a bit of a snag. The box I have "expired" in 2002 but they
are in sealed plastic bags (well those that haven't started to
biodegrade are...) and my main use is for dust protection rather than
fumes.

Also there were so many different filters to choose from; I wasn't sure
which ones to buy. What do you fit to your mask?

3M 2128, these are P2 particulate and "nuisance level" organic vapour
and acid gases. A google will probably find what size particulates a
P2 or P3 filter deals with and what the other filter codes mean.

The fact that this is a disposable filter made me delay buying it
because it seemed expensive to buy it and throw it away a month later
but I think the monthly rule is only for business use

Yes that is the H&S rules that really only apply to business use.
Common sense in the DIY enviroment. If I was to do something "fumey"
I'd chnage the filters for new ones from one of the sealed bags and
pay attention for any detectable niffs whilst in use.

only I am not sure when I will know it is time to replace it. Perhaps
the strap will fall off ...

The plastic frame of mine has snapped in a couple of places, stitched
back together and taped up, failed again. SWMBO'd has replaced it
with two bits of flat elastic.

or the filters will be black and I will know it's time to buy a new one!

Only if your dust is black...

--
Cheers
Dave.