Buying Guide

How to Choose a Room Air Cleaner


How to Choose a Room Air Cleaner

When you consider that most Americans spend 90% of their time indoors, it makes sense that indoor air quality can impact quality of life. If you’re concerned about indoor air quality, or you want to improve the indoor air quality in your home, this guide is for you.

To help you choose the right product, we will discuss how air cleaners operate, and how they measure performance. We’ll also look at the different pollutants that can impact your air quality, and how a room air cleaner works to remove them.

All About Indoor Air Contaminants

There are a variety of things that can impact indoor air quality. Some of these contaminants are visible, while many are not. Depending on which part of the country you live in, you may be uncomfortably familiar with visible air pollutants. Consider the escalating effects of forest fires. Smoke and ash from these fires may have migrated to homes thousands of miles away. Meanwhile, everyday particulates like pollen can also invade homes. While seasonal pollen does less damage than smoke and ash, it can trigger asthma and allergies in individuals with heightened sensitivity.

Other contaminants are invisible to the naked eye but can be equally or more harmful to human health than visible pollutants. Other pollutants are emitted from indoor sources and activities such as cooking, cleaning, secondhand smoke, building materials, consumer products and home furnishings. According to the EPA, the effects of pollutants can range from annoying to life-threatening depending on the source.

The best way to improve indoor air quality is to reduce sources of pollutants and ventilate with clean, outdoor air. In addition, using a portable air cleaner, or air purifier, can further improve indoor air quality. When used properly and combined with other best practices recommended by the CDC and other public health agencies, air purifiers can even reduce airborne pathogens in a home, such as the virus that causes COVID-19.

All About Indoor Air Cleaners

Room air cleaners use a variety of filtration methods to purify your indoor air. Many models incorporate fans to move air along with a combination of filters to catch and clean the air. High-efficiency particulate air (HEPA) filters are one type of filter used to catch particles. Activated-carbon filters are designed to remove gases, and electrostatic filters or precipitators attract particles to purify the air.

Depending on the product, air cleaners may run automatically or manually. Air cleaners that have an auto setting use sensors to adjust the speed of filtration in a space. Other models include multiple speed settings to allow users to choose and control the speed at which the air is filtered. While high fan speeds and long run times clean more air, they also require more energy, making it even more important to find an energy-efficient model to save money while cleaning your indoor air.

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

What to Consider When 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. 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.

Clean Air Delivery Rate Table

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.