How Often Should You Change Your Merv 13 Filter?

For Merv 8, 11 and 13 filters, it is recommended that you change the filter at least every 3 months for optimal filtration and healthier air in your home. However, during the spring and fall months, the filter usually doesn't get as dirty due to the lack of need for heating and cooling, so you can get by without changing it as often. On the other hand, filters that normally last 90 days should be changed every 30 days during the peak summer and winter months when HVAC systems are operating at their maximum capacity. If chemical disinfectants are used, they should only be applied with the HVAC system turned off and should not be applied to ventilation filters before continuing to use them within ventilation systems.

The effects of disinfectants on filter performance are unknown, so filters should only be treated with disinfectants if they are to be removed from service and discarded. UV systems are quite effective in maintaining the cleanliness of HVAC coils, drain trays, and other wet surfaces. These systems generally require more lamps so that they can provide significant UV doses in a short period of time. A typical single-pass inactivation efficiency is 85%, much like that of a good particulate filter, but systems can also be designed for inactivation greater than 99.9%.

CDC has approved wall-mounted devices for use in tuberculosis control for nearly 20 years and there is guidance from NIOSH on how to design them. Mobile UV systems are frequently used for terminal cleaning and surface disinfection in healthcare and other spaces. All three types of systems may be relevant, depending on the type of building and the individual spaces within the building. The design and sizing of effective ultraviolet disinfection systems can be a complex process because of the need to determine the dose administered to a moving air stream or to an irradiated region of a room.

Inlet systems are further complicated by the configuration of the air treatment unit and ducts and reflections from surfaces, which can help achieve higher levels of irradiation. Upper air systems require an adequate air mix to function properly and, at the same time, pay close attention to reflective surfaces that could cause room occupants to be overexposed to UV energy. Accredited system manufacturers and designers can help by making the necessary calculations and designing specific systems for individual spaces. With more than 57,000 members from more than 132 countries, ASHRAE is a diverse organization dedicated to promoting the arts and sciences of heating, ventilation, air conditioning and refrigeration to serve humanity and promote a sustainable world. Our MERV 3 air filters of 1, 2 and 4 are designed to last approximately 3 months, while our MERV 13 replacement filters for the whole house must be replaced every 6 months. If you have pets, children, or people with allergies in your space, we recommend that you change your filters more frequently as it is important to replace filters regularly due to their decreased efficiency over time. The average MERV efficiency range of 5 to 10 will likely require filter changes in about two to three months.

If you use the air filter for less than five hours a day, you can extend the life of the filter to a few more months. But what happens if you let that time go by a little? Changing your air filter is the easiest and most effective way to maintain your home's cooling and heating system. If you're still not sure when you should change your air filter, consider all factors such as dust accumulation, pet hair buildup, allergens present in your space, etc., as well as specific recommendations on the packaging.

Clint Bouyer
Clint Bouyer

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