Recently, my husband did some maintenance work on our car before a family road trip. One of the things on his list was changing the air conditioning filter in our van. After he removed the filter, he showed it to me. It was an absolute nightmare – black with several years' accumulation of dust and pollution. It could not possibly have been effective in purifying our car's air. Furthermore, I suspected that the musty odor I smelled from time to time might have come from this dirty filter.

Upon doing a little bit of research, I found that this was in fact the case. A site that helps with do-it-yourself car repair, 2carpros.com, cites the following as two common problems with car air cabin filters:

• Air cabin filter becomes plugged not allowing air flow into the vehicle cabin.
• Air cabin filter becomes moist creating mildew and odors.

Of course, breathing unclean air in such a confined space as a closed vehicle is hazardous, especially to those who are particularly sensitive due to allergies or asthma. The next time you take your car in for an oil change, be sure to ask the service people to check your car's air conditioning filter. Just like any other filter, it needs regular replacing in order to be effective in helping you breathe better.