# ICC-500T Program Mode

**URL:** <https://community.inkbird.com/t/icc-500t-program-mode/52131>\
**Category:** Questions & Answers\
**Created:** [May 22, 2023, 6:51am UTC](https://community.inkbird.com/t/icc-500t-program-mode/52131 "2023-05-22T06:51:20Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Sally](https://yyz1.discourse-cdn.com/flex031/user_avatar/community.inkbird.com/sally/32/362_2.png) [@Sally](https://community.inkbird.com/u/Sally)\
**Post date:** [May 22, 2023, 6:51am UTC](https://community.inkbird.com/t/icc-500t-program-mode/52131/1 "2023-05-22T06:51:20Z")

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How to switch program mode from work1 to work2?

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**Author:** ![Tania](https://yyz1.discourse-cdn.com/flex031/user_avatar/community.inkbird.com/tania/32/88_2.png) [@Tania](https://community.inkbird.com/u/Tania)\
**Post date:** [May 23, 2023, 3:18am UTC](https://community.inkbird.com/t/icc-500t-program-mode/52131/2 "2023-05-23T03:18:57Z")

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Hello,  
It depends on the reading and settings of the ICC-500T.  
The ICC-500T works in the following ways:  
CS is the CO2 target value.  
HD is the lowest acceptable deviation from the target value.  
CD is the highest acceptable deviation from the target value.  
When the CO2 reaches or falls below the CS-HD value, the CO2 generator (work1) turns on until the CO2 reaches the CS value. When CO2 reaches or above the CS+CD value, the exhaust fan (work2) switches on until CO2 reaches the CS value.