Blaine,

You might ask Bofa if their filter clogged warning includes the chemical filter. My guess is it doesn't. They probably measure back pressure in the air flow to spot a clogged physical filter.

More typical with a chemical/charcoal filter is to weigh the charcoal. As it absorbs the chemicals it gains weight. I used to live on top of a live volcano in HI and we used a filter that removed sulphur dioxide from the air in our house. The rule of thumb for that filter was that when the charcoal gained 20% of its starting weight it was pretty close to spent and should be replaced.

This is based more on gut feeling than anything. But I don't want "stuff" going into my lungs if I can reasonably prevent it, particulates or gases. It is not worth the risk. I have grown fond of breathing and don't want to become one of those old folks sitting on stools in Las Vegas, pulling the handles on the slot machines while they suck on O2 through a nasal cannula (and smoke at the same time of course....by then the damage is done....what the heck?)

Ernie! It sounds like you are describing the industrial version of a Hookah! <grin> You might try marketing those in marijuana friendly Washington and Colorado! <grin>

Dave