The life span of the filters that remove contaminants from the air is critically important. The filter life of an air purifier depends upon a variety of factors. These include filter type, size and usage. Many large HEPA filters can last for 5 years under the right conditions. However, in places with larger amounts of particulate matter in the air, 2-3 years is more realistic. On the other hand, the average lifespan of carbon filters is generally 3 to 5 years.