I've used one for the past 2 years since I live and work in a dust bowl. They do an excellent job in keeping dust out of the cab and help with alergies. But they significantly reduce the flow of air that the fan can draw. They don't block odors once the activated carbon gets wet for the first time, but they hold up remarkably well. I change mine about every 6 months and I've driven through dust storms so bad I had to pull off the road. The filters would probably last at least a year under normal conditions. Good product!