How to Choose a Room Air Cleaner

Clean air is not just important for the outdoor environment, it is important for your indoor living space. Follow the guidance below to help you choose the right room air cleaner.

Why Should I Buy a Room Air Cleaner?

Choosing the right portable room air cleaner (or air purifier) can help improve indoor air quality for you and your family. Indoor air contains pollutants that can affect human health and cause symptoms such as asthma and allergies. Some pollutants, such as wildfire smoke and pollen, can come from outdoors. Other pollutants are emitted from indoor sources and activities, such as cooking, cleaning, secondhand smoke, building materials, consumer products, and home furnishings. The best way to improve indoor air quality is to reduce sources of pollutants and to ventilate with clean outdoor air. However, using a portable air cleaner can help improve indoor air quality. When used properly and combined with other best practices recommended by CDC and other public health agencies, room air cleaners can also help reduce airborne pathogens in a home, such as the virus that causes COVID-19.[1]

For guidance about what to look for when choosing an air cleaner for your home, check out the steps below.

How Does a Room Air Cleaner Work?

Room air cleaners can use a variety of filtration methods to purify your indoor air. Many models use fans along with a combination of filters, such as High-Efficiency Particulate Air (HEPA) filters, that catch particles, and filters designed to remove gases, such as activated carbon filters. Others use electrostatic filters or precipitators that attract particles to purify the air.

Some air cleaners have an auto-setting, using sensors to adjust the speed of filtration in a space. Other models offer multiple speed settings that users manually select to choose the speed at which the air is filtered. Higher fan speeds and longer run times will increase the amount of air filtered, which will typically increase the amount of clean air.[2] With long run times comes significant energy use, making it even more important to find an energy-efficient model to save money while cleaning your indoor air.

In addition, some units are marketed as having quiet operation because they do not have a fan. However, units that do not have a fan are typically much less effective.[3]

What Should I Consider in Purchasing a Room Air Cleaner?

1. Find Your Room Size

Portable room air cleaners are designed to filter the air in a single room or area. Because there are many sizes of room air cleaners, determine the square footage of the room where you will use the room air purifier most often. Many devices specify a Clean Air Delivery Rate (CADR). Following the table in the next section, you can select a model with the CADR that aligns with the square footage of your room. Larger models use more energy, so unless you experience frequent, high air pollution events like wildfire smoke, choose a model that is sized appropriately to fit your room for the most efficient air purification. Oversizing your room air cleaner can result in paying a higher initial cost and increased operating costs (from increased energy consumption to  more expensive filter replacement).

2. Review the Clean Air Delivery Rate

The CADR measures how quickly a unit delivers filtered air and can be used to measure the performance of a room air cleaner. The higher the CADR, the larger the area the air cleaner can serve. It is important to select a room air cleaner specific for your room size. A general rule to consider is the “2/3 rule” – find an air cleaner with a CADR that is at least 2/3 the square footage of the space. Use the table below to help estimate which air cleaner is right for your home.

Note: CADRs are calculated based on an 8-foot ceiling; if you have higher ceilings, you may want to select an air cleaner with a higher CADR. The CADR listed is based on the CADR required to remove 80% of smoke particles, assuming one room air exchange per hour, and the rating is typically measured at the air cleaner’s highest speed.

CADRs for air cleaners are measured across three common particulate types – smoke, dust, and pollen. Think through the following considerations in understanding which CADR(s) – smoke, dust, pollen or all three – may be most relevant for you:

Allergies: If you suffer from allergy symptoms, check the CADR for the particulates most relevant to your allergies—dust, pollen, or smoke. For example, if you have spring allergies and live in an area with high pollen count, look for air cleaners with a high pollen CADR.

Please note that room air cleaners, by themselves, may not address all allergy issues within a home, and additional remediation steps may be required. For example, some large allergens may settle out of the air quickly and accumulate on surfaces like furniture or floors before they reach an air cleaner, which may be addressed through regular vacuuming, mopping, and dusting. Another example is mold, which requires removing the moisture source to clean up the mold and to prevent further mold growth.

COVID-19: By itself, air cleaning or filtration is not enough to protect people from COVID-19. But when used properly along with other best practices recommended by CDC, air purifiers can be part of your plan to reduce the potential of airborne transmission indoors¹. Be sure it meets at least one of the following criteria on the air cleaner packaging, label, or website description:

1. The filter is designated as High-Efficiency Particulate Air (HEPA),
2. It has high CADR rating for smoke (vs. pollen or dust) because smoke has a smaller particulate size than pollen or dust,
3. The manufacturer states that the device will remove most particles in the size range below 1 µm.

Wildfires: You may decide to purchase an air cleaner as part of your preparation for a wildfire emergency to help improve your indoor air quality during a wildfire smoke event. If you experience frequent, very high smoke concentrations, you may want to purchase an air cleaner with a higher CADR than suggested in the table above.

3. Ensure the Air Cleaner Does Not Emit Ozone

Some air cleaning technologies may emit ozone, which is a known lung irritant. In fact, there are products called ozone generators, that intentionally generate ozone, that are marketed as air cleaning devices. Even small amounts of ozone can cause chest pain, coughing, shortness of breath, and throat irritation.[1] All ENERGY STAR certified products are third-party verified to not exceed safe levels of ozone generation.

4. What is Air Changes per Hour (ACH)?

Air changes per hour (ACH) is another metric sometimes reported by the manufacturer. ACH primarily measures ventilation – or how fast air is added and removed, or exchanged – in your home or room in an hour. Higher amounts of ventilation help to remove particulates and other pollutants; however, air cleaners don’t actually ventilate. Modern homes are designed and built to reduce energy loss so your home maintains its temperature as efficiently as possible, and as such, we add ventilation into homes through vent fans in kitchens and bathrooms, energy-recovery ventilators, or opening a window. Adding a room air cleaner into your space simulates ventilation by removing most particulates from the air that passes through the device. The rate at which air is treated by an air cleaner can also be measured as ACH, for a specified room size.

EPA recommends looking for air purifier models that provide at least 4.8 ACH for the recommended room size to help improve your indoor air quality. A device labeled to provide 4.8 ACH in a 10’x12’x8’ room can treat the air in a room of that size 4.8 times each hour. In general, a device with much higher ACH for a room is not recommended, as it provides minimal air quality improvements for higher energy costs.

It is important to note that claims regarding ACH and CADR have not been substantiated unless the product has been tested to the ANSI/AHAM AC-1 test method through a program that third-party verifies products such as the ENERGY STAR program.