# Keep state of sensor
**URL:** https://discourse.nodered.org/t/keep-state-of-sensor/59074
**Category:** General
**Created:** [27 February 2022 17:03 UTC](https://discourse.nodered.org/t/keep-state-of-sensor/59074 "2022-02-27T17:03:25Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Chura](https://discourse.nodered.org/u/Chura)
#### Post date: [27 February 2022 17:03 UTC](https://discourse.nodered.org/t/keep-state-of-sensor/59074/1 "2022-02-27T17:03:26Z")
Hi
I have a contact sensor, that tell me if something stop the rollercoaster from shutting down.
I want to add, that send the command on the right, only if other sensor is closed
However, That other sensor report to MQTT, and I cannot query MQTT for current state. I need to keep that as a variable or flag, that I can query during my flow.
How can I achieve that functionality ?
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### Author:  [@Sean-McG](https://discourse.nodered.org/u/Sean-McG)
#### Post date: [27 February 2022 18:48 UTC](https://discourse.nodered.org/t/keep-state-of-sensor/59074/2 "2022-02-27T18:48:45Z")
You could use a change node to store the state in a flow variable, when a message comes from MQTT.
Then in a switch node check the value of the flow var.
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### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [13 March 2022 18:49 UTC](https://discourse.nodered.org/t/keep-state-of-sensor/59074/3 "2022-03-13T18:49:36Z")
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