# PM 2.5 cf Analysis

**URL:** <https://community.purpleair.com/t/pm-2-5-cf-analysis/10326>\
**Category:** Data\
**Created:** [September 24, 2024, 6:17am UTC](https://community.purpleair.com/t/pm-2-5-cf-analysis/10326 "2024-09-24T06:17:34Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![Kieran](https://sea2.discourse-cdn.com/flex020/user_avatar/community.purpleair.com/kieran/32/6220_2.png) [@Kieran](https://community.purpleair.com/u/Kieran)\
**Post date:** [September 24, 2024, 3:21pm UTC](https://community.purpleair.com/t/pm-2-5-cf-analysis/10326/2 "2024-09-24T15:21:33Z")

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Hi @KevinChess

A majority of PurpleAir models contain two laser counters that take two individual PM measurements. More information is available here: [What are Channel A and Channel B?](https://community.purpleair.com/t/what-are-channel-a-and-channel-b/3643) The exact answer to your question depends on where you’re getting the data: through the API or from an SD card.

**If you’re getting data from an SD card:**  
pm2\_5\_cf\_1 is the data from the “A” channel, while pm2\_5\_cf\_1\_b is the data from the “B” channel.

**If you’re getting data through the API**  
pm2\_5\_cf\_1\_b would be the data from the “B” channel. However, pm2\_5\_cf\_1 would be the average of the “A” and “B” channels.

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_[View the full topic](https://community.purpleair.com/t/pm-2-5-cf-analysis/10326)._