Recently, two different techs have told me stories about finding dryer sheets used creatively in customers air conditioning systems. When they asked their customer why there were bunches of dryer sheets stuck to the air filter, the customer said they liked the “clean, fresh scent.” Another story involved customers removing supply registers and stuffing dryer sheets across the outlet of the register to “filter and freshen” the air. Naturally, some of these found their way to the coil where they clogged the coil and caused enough air flow restriction to freeze the system up. In all cases, dryer sheets stuffed into clever places only serve to restrict the airflow. Even if they did not, all you are accomplishing is introducing whatever chemical is on them into your system. They don’t remove odors – they just add more. Honeywell used to sell a system to do that called the “Scentrol.” Scentrols used little gel cans that looked like sterno. They system controlled how much air circulated over the can to regulate the scent. It even had a wall control. My father sold one to a customer who also bought an electronic air cleaner with an activated charcoal filter to remove smells. The customer insisted on having the Scentrol installed, even after dad explained that they were buying one machine to put smells in the air and another to take them out. Here is a link to an online forum that has a picture http://www.hvacproforums.com/threads/honeywell-scentrol.1148/
So what do you suggest to customers who want the air conditioner to improve their home’s odor? I don’t think you can buy a Scentrol anymore. First, try to find out if there are specific odors they are trying to get rid of. Finding and eliminating the source is really the best option. My brother once discovered that the kitchen sink drain leaving the disposal had never been connected on a new house in which the customers were complaining about dirty sock syndrome. If the odors are system related, look at the condition of the indoor coil and make sure there are not problems such as a leaky return in a crawl space. If they just like the idea of having a “fresh scent” system there are a number of filters that use activated charcoal to absorb odor. Just check that the pressure drop across the filter is not too high. Like the famous 1” pleated filters, some of the charcoal filters can add enough restriction to cause an airflow problem even when they are clean. Another option would be an air cleaner that uses titanium dioxide and UV light to eat up compounds that cause odors. Both Field Controls and Lennox make air cleaners that use this technology. Now you are on the high end of the cost spectrum, but you are dealing with solid, reputable companies who sell things that work.