How to Choose 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. Therefore, the first step in finding the right product for you is knowing your room size. You will need to determine the square footage of your room. You will also need to know the approximate ceiling height of your room.

It’s important to find an air cleaner that is the right size for your room. Buying a unit that is too small may impact performance, while a unit too large will result in paying a higher initial cost and increased operating costs. Unless you experience frequent, high air pollution events like wildfire smoke, always choose a right-size model.

2. Review the clean air delivery rate.

Many devices measure performance using a metric know as Clean Air Delivery Rate (CADR). CADR is based on square footage plus an average ceiling height of eight feet. 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.

There are two things to consider about CADR. First, CADRs are calculated based on an eight-foot ceiling; if you have higher ceilings, you may need a product with a higher CADR. Second, the CADR listings are 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.

Likewise, if smoke, dust and/or pollen are most relevant to you, consider this advice from the EPA:

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, so 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 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 the CDC, air purifiers can be part of your plan to reduce the potential of airborne transmission indoors. Be sure it meets at least one of the following criteria on the air cleaner packaging, label or website description:

• The filter is designated as high-efficiency particulate air (HEPA).
• It has a high CADR rating for smoke (vs. pollen or dust) because smoke has a smaller particulate size than pollen or dust.
• The manufacturer states that the device will remove most particles in the size range below one 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. 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)?

Ventilation is another factor affecting indoor air quality. Air changes per hour (ACH) primarily measures ventilation and is another metric sometimes used to differentiate air cleaners. While ventilation is good for air quality, it is not a long-term solution for controlling indoor air quality. Whenever air is let in, or air escapes, energy is wasted. If you’ve ever accidentally left a window open in winter, you know the impact it can have on your comfort and utility bill. That’s why today’s homes are intentionally designed to control ventilation through the addition of vents, fans and windows.

While air cleaners don’t actually ventilate, they simulate the process. By removing most particulates from the air that passes through the device, air cleaners offer the same benefits as ventilation. Therefore, some products list the ACH rate for a specified room size to demonstrate the rate at which the air is treated by the air cleaner.

The 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.

5. Look for the ENERGY STAR!

Air cleaners that are ENERGY STAR-certified can help you improve your indoor air quality, save money and help the planet! ENERGY STAR-certified room air cleaners are 27% more energy-efficient than standard models. ENERGY STAR products are independently certified based on testing in an EPA-recognized lab to ensure they save energy and money without sacrificing performance. Specifically, ENERGY STAR measures energy efficiency by using a CADR-to-watt ratio, which means certified air cleaners must deliver the same amount of filtered air as a standard model while also using less energy.

If all room air cleaners sold in the United States were ENERGY STAR-certified, the energy cost savings would grow to more than $400 million each year, and more than 9 billion pounds of greenhouse gas emissions would be prevented, which is equivalent to the emissions from nearly 900,000 vehicles.

Start Shopping for an Air Cleaner

When you’re ready to find the best air cleaner for your home, be sure to check out the wide variety of ENERGY STAR-certified air purifiers at The Home Depot. And to find available rebates in your area, refer to the ENERGY STAR Product Finder.

Using Your Room Air Cleaner

• Check the filter.If the filter is dirty, it won’t work as well. Review the product manual for recommendations on how often to replace the filter.
• Placement.Read the product manual or instructions on where to place your room air purifier to achieve optimum performance. Make sure the airflow is not obstructed. Keep air cleaners away from curtains and items that might block airflow.

This project is based on content authored by ENERGY STAR.