WHEELER ON HVACR: You And IAQ - Part 3: Tobacco Smoke
Probably the hardest IAQ pollutant to get rid of is tobacco smoke, because there are so many components. There’s what can be seen, the carbon and tars, and what can’t be seen, the odors of aldehydes and many other irritants. And that’s why high-quality air filters just can’t do the job; because all they remove are the solid particles.
My son, who is a musician, had to play in a casino a couple of weeks ago, and he and the entire band complained about all the cigarette smoke. And although the casino (like almost every bar you might enter) has good air filtration, that simply isn’t enough, for although you may not be able to see the smoke, the strong odor is still there and quite objectionable.
What an electronic air filter does well is to clear the air and reduce the accumulation of smoke residue on all exterior surfaces of the building…you know, that yellowing of the walls and ceiling. And if you add an activated charcoal filter, that does help a bit, but as any qualified mechanical engineer can tell you, the only way to solve the problem of objectionable cigarette smoke is frequent introduction of 100% outside air, which is very costly from an energy standpoint.
Bringing in 100% outside air is very easy to do, you just connect the system air return to the outdoors, and then provide points to exhaust the smoky air outside. But, the air conditioner might require twice the capacity to do the job (depending on the location), doubling its cost and raising the energy bill twice as high…I guess the casino that my son played at wasn’t willing to buy into that.
Are there any energy-saving alternatives to this? Yes, there are! There are systems and devices that are manufactured for commercial, industrial and institutional buildings that can reclaim much of the energy from the exhausted air, but they’re not 100% efficient, and they add significantly to the cost of the equipment (they aren’t cheap).
There are devices that are designed with porous heat exchangers that take the energy from exhausted air and return it to the entering air, and, for those who just want a greater introduction of outdoor air, air conditioners that retrofit into the existing outdoor-air intake, then recover the energy from the exhausted air. These, of course, boost the capacity (and the energy consumption) of an existing system to handle the increased introduction of outdoor air, without a need to replace the whole system.
But, what can be done for homes where people smoke and they don’t like the odor or the damage caused to interior surfaces by the accumulation of tars? I doubt that any homeowners would stand for bringing in 100% outdoor air to solve the problem (perhaps Bill Gates?), so some compromise is usually required.
I remember back when I was an HVAC contractor, having to clean the electronic air filter of a couple who smoked heavily…it looked like someone had poured dark molasses over the plates, and it smelled awful! But it did remove all the solids successfully, so part of the job was done.
The other half of the job - which not only solves the tobacco smoke problem, but also other IAQ problems - has come on the market from several sources over the past 10 years or so. These are residential ventilation devices that introduce a constant flow of outdoor air and then recover the energy from the exhausted air, so not much is lost.
They seem a bit costly to me, since they consist of just a fan box with a porous heat-exchanger surface (to allow an interchange of both temperature and humidity). And since they usually operate independent of the HVAC system, they require the installation of ductwork, diffusers and a separate electrical connection, so there are considerable installation costs. But for people with severe allergies, they can be a godsend.