# ‘K’ Calibration Factor Of PurpleAir Flex? **URL:** \ **Category:** Community Projects\ **Created:** [February 5, 2025, 3:03am UTC](https://community.purpleair.com/t/k-calibration-factor-of-purpleair-flex/11537 "2025-02-05T03:03:27Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![dwhitemv](https://sea2.discourse-cdn.com/flex020/user_avatar/community.purpleair.com/dwhitemv/32/1508_2.png) [@dwhitemv](https://community.purpleair.com/u/dwhitemv)\ **Post date:** [February 5, 2025, 8:46pm UTC](https://community.purpleair.com/t/k-calibration-factor-of-purpleair-flex/11537/2 "2025-02-05T20:46:37Z")
PurpleAir sensors are not appropriate to use as a reference sensor. There is too much interference from Plantower’s “adjustments”. If anything, you’d use the Temtop to create adjustment curves for the PurpleAir, as the responsiveness characteristics of the Temtop are (likely) published by the manufacturer and that can be used to create the K factor(s) to adjust it to a reference source (FRM/FEM or whatever is appropriate for your environment). I’d recommend reviewing the papers posted in Lance’s thread, linked below, to understand the procedure. > [@Calibration of PurpleAir monitors](https://community.purpleair.com/t/calibration-of-purpleair-monitors/482): > > For the last few years, I’ve been analyzing the performance of the PurpleAir monitors. Last week the Sensors journal published my detailed comparison of the Plantower CF\_1 algorithm with an alternative algorithm called ALT-CF3. This is Open Access. There is also a link within the pdf that takes you to the Supplemental Information (pictures of the PurpleAir and SidePak research-grade monitors, for example.) ALT-CF3 is a based on a method that has been used for decades to calculate PM2.5 from… --- _[View the full topic](https://community.purpleair.com/t/k-calibration-factor-of-purpleair-flex/11537)._