aluminized or galvenized? if it's galvenized you may be breathing in the dross fumes and that is realy bad it makes you fill like you have pneummonia it's basicly killing your lungs.

Bogieman,

If you have sesitive lungs, which you would if you have asthma, then any of the fumes and dusts associated with welding and shops in general are going to give you problems with your breathing.  If you like what you are doing then beyond trying to persuade the others to use their exhaust systems you probably need to consider a positve flow hood/respirator system or at least a good respirator.  There are several low profile ones that will fit under your hood. I have preferred the ones with hoses to a filter pack on my belt on my back.  Keeps the filters away from more of the dust and smoke so they don't need as much replacing.

The aluminized pipe should not be nearly as bad as galvanized but will put off fumes that are affecting you lungs.  Good luck.

Have a Great Day,  Brent