You can usually clean replaceable HEPA filters about once a month and replace them every four to six months. The only exception to replacing a HEPA filter when it's dirty is if you have an air system that has a prefilter in front of the HEPA filter. This prefilter will capture some of the dust and larger particles, and some of these prefilters are washable so that they can remove the dust and dirt that they accumulate. However, this is not the real HEPA filter.
Experts agree that HEPA filters should always be replaced when dirty and not cleaned. The frequency of cleaning or replacing your HEPA filter will vary from house to house, depending on how often the air purifier is used and how dirty the air is. Generally, manufacturers recommend changing or cleaning the filter every three to six months to enjoy the full benefits of air purifiers. If you have one of the best air purifiers for allergies, the recommended frequency is one to two months.
Some filters are designed to last longer, for example, the filter on a Dyson Pure Cool device is valid for one year. If you notice a musty smell, it could indicate that the HEPA filter is faulty and you need to change it. You should also inspect your air purifiers regularly, and if the HEPA filter appears to be damaged, you should replace it immediately. Some products, such as the Honeywell Insight portable air purifier, have systems designed to tell you when a filter needs to be replaced.
Commercial or sanitary HEPA filters must meet a specification established by the United States Department of Energy and be capable of filtering at least 99.97% of 0.3 micron particles (one millionth of a meter). Not all air purifiers come with washable filters or permanent filters that can be cleaned with a vacuum. But if you use an air purifier in a commercial or healthcare environment, you'll be using a much larger, more powerful air purifier to clean the air in a much larger space. Occasionally rinsing the filter with purified water after cleaning it can help extend the life of a washable filter.
However, unless explicitly recommended by the manufacturer, you should avoid cleaning the HEPA filters yourself. Consult the air purifier manufacturer for the most reliable guide on when you should change your HEPA filter.
