{"id":5075,"date":"2025-09-03T19:31:36","date_gmt":"2025-09-03T11:31:36","guid":{"rendered":"https:\/\/smartairfilters.com\/?p=5075"},"modified":"2026-03-09T14:41:14","modified_gmt":"2026-03-09T06:41:14","slug":"cadr-airflow-difference","status":"publish","type":"post","link":"https:\/\/smartairfilters.com\/en\/blog\/cadr-airflow-difference\/","title":{"rendered":"What\u2019s CADR and What’s the Difference With Airflow Rate?"},"content":{"rendered":"

If you\u2019re buying an air purifier, you might see the terms \u201cairflow\u201d and \u201cCADR\u201d used interchangeably to describe purifier performance. But what\u2019s the difference between CADR (clean air delivery rate) and airflow? Are they the same thing? Or which one \u2013 CADR vs. airflow \u2013 should you use to choose a purifier?<\/p>\n\n\n\n

What Does CADR Mean?<\/strong><\/h2>\n\n\n\n

CADR is an estimate of how much clean air a purifier puts out. You\u2019ll see CADR report this volume in cubic meters per hour (m\u00b3\/h) or cubic feet per minute (CFM). The Association of Home Appliance Manufacturers (AHAM)<\/a> was the first to define CADR, and air purifier companies widely recognize this standard. <\/p>\n\n\n\n

Are CADR and Airflow Rate the Same Thing \u2013 Short Answer<\/strong><\/h2>\n\n\n\n

In short, CADR and airflow are not the same thing. They are slightly different measurements. That means we should not compare CADR values from one air purifier to the airflow values from another air purifier. We\u2019ll get into that later.<\/p>\n\n\n\n

Read More: How we test out air purifiers at Smart Air<\/a><\/p>\n\n\n\n

What\u2019s the Difference Between CADR and Airflow Rate \u2013 Long Answer<\/strong><\/h2>\n\n\n\n

The real answer gets into some nerdy (but actually interesting!) details about how people measure CADR and airflow. Here\u2019s what you need to do for a CADR test:<\/p>\n\n\n

\n
\"\"<\/figure><\/div>\n\n\n

Steps to Test an Air Purifier\u2019s CADR<\/h3>\n\n\n\n

Step 1: <\/strong>Pollute a sealed room to crazy high pollution levels (normally by burning cigarettes).<\/p>\n\n\n\n

Step 2: <\/strong>Run your purifier.<\/p>\n\n\n\n

Step 3:<\/strong> Take PM2.5<\/a> concentration readings every 2 minutes for 20 minutes.<\/p>\n\n\n\n

Step 4:<\/strong> Use these numbers to work out the rate of purification of the room (the CADR).<\/p>\n\n\n\n

The hard part about doing this test is that you need a lot of complex equipment, a large testing room, the time and patience to do the test, and some data analysis skills.<\/p>\n\n\n\n

Testing Air Purifier Airflow Rate<\/p>\n\n\n\n

To measure airflow, the only thing you need is a wind speed measure (fancy name \u201canemometer\u201d):<\/p>\n\n\n

\n
\"\"<\/figure><\/div>\n\n\n

Steps to Test Air Purifier Airflow Rate<\/h3>\n\n\n\n

Step 1:<\/strong> Place the anemometer against the filter and look at the number.<\/p>\n\n\n\n

Step 2:<\/strong> Multiply this speed by the area of your filter.<\/p>\n\n\n\n

That\u2019s it! So much easier. (OK, OK, technically you can get more complicated by measuring multiple points around the filter or even putting a large hood around the purifier to measure airflow.)<\/p>\n\n\n

\n
\"\"<\/figure><\/div>\n\n\n

This method works all right, but it has a problem. Since this method only measures wind speed, it only tells us how much air is coming out.<\/p>\n\n\n\n

What Airflow Tests Don\u2019t Tell Us<\/h3>\n\n\n\n
    \n
  1. How clean is that air coming out?<\/li>\n\n\n\n
  2. Is any of that air actually coming in from a leak or the middle of the air vortex and then being pushed back out?<\/li>\n\n\n\n
  3. How efficiently is the machine mixing that air in the room?<\/li>\n\n\n\n
  4. How much of the air that comes out of the purifier gets sucked back into the machine quickly, rather than being pushed farther out into the room?<\/li>\n<\/ol>\n\n\n\n

    Read More: Can you convert airflow to CADR?<\/a><\/p>\n\n\n\n

    All four of those variables will influence how well your air purifier will clean your room. And an airflow number won\u2019t tell us that. That\u2019s why people go through all the hassle of burning cigarettes and using up filters to measure CADR.<\/p>\n\n\n

    Bottom Line<\/div>
    Bottom Line: Airflow vs. CADR<\/div>
    Airflow estimates the amount of air purifiers move, whereas CADR estimates the rate at which the purifier delivers clean air. Since they are based on different testing standards, the values are not directly comparable.<\/div>
    Smart Air<\/div><\/div>\n\n\n\n

    <\/p>\n\n\n\n

    Comparing Air Purifiers Before Making a Purchase<\/h3>\n\n\n\n

    How to choose: <\/strong>When comparing purifiers, look for CADR over airflow (and pay attention to whether the company is reporting one or the other). Airflow numbers usually come from the purifier manufacturer, whereas CADR tests sometimes come from third-party testing organizations, which can be more trustworthy. <\/p>\n\n\n\n

    Learn more: The Four Steps to Choosing the Best Air Purifier \u00bb<\/a><\/p>","protected":false},"excerpt":{"rendered":"

    If you\u2019re buying an air purifier, you might see the terms \u201cairflow\u201d and \u201cCADR\u201d used interchangeably to describe purifier performance. But what\u2019s the difference between CADR (clean air delivery rate) and airflow? Are they the same thing? Or which one \u2013 CADR vs. airflow \u2013 should you use to choose … <\/p>\n

    Read more<\/a><\/p>\n","protected":false},"author":1035,"featured_media":41235,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_relevanssi_hide_post":"","_relevanssi_hide_content":"","_relevanssi_pin_for_all":"","_relevanssi_pin_keywords":"","_relevanssi_unpin_keywords":"","_relevanssi_related_keywords":"","_relevanssi_related_include_ids":"","_relevanssi_related_exclude_ids":"","_relevanssi_related_no_append":"","_relevanssi_related_not_related":"","_relevanssi_related_posts":"11976,22290,13492,4247,19028,21604","_relevanssi_noindex_reason":"","footnotes":""},"categories":[190,259],"tags":[383,283,224,205],"class_list":["post-5075","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-air-purifiers","category-filters","tag-air-filters","tag-air-purifier","tag-airflow","tag-cadr","resize-featured-image"],"acf":[],"_links":{"self":[{"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/posts\/5075","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/users\/1035"}],"replies":[{"embeddable":true,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/comments?post=5075"}],"version-history":[{"count":23,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/posts\/5075\/revisions"}],"predecessor-version":[{"id":38805,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/posts\/5075\/revisions\/38805"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/media\/41235"}],"wp:attachment":[{"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/media?parent=5075"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/categories?post=5075"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/smartairfilters.com\/en\/wp-json\/wp\/v2\/tags?post=5075"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}