I have the Sparkfun QWIIC-enabled BME688 gas/environment sensor, and I’d like to use this in a greenhouse environment where it will be exposed to fairly high humidity and varying temps. Normally for this kind of application, I’d apply a silicone conformal coating to the PCB and components.
However, given all of the dire warnings about not touching the metal case of the BME688, etc., I’m wondering if there’s any concerns about applying a conformal coating (or even cleaning this board with alcohol), if exposing the gas sensors to close-proximity solvents could permanently damage something??
To be clear, I don’t intend to coat the sensor itself. I’m mostly concerned about whether it could be damaged by applying such a coating to the REST of the board, around the central sensor?
I think there are 2 main reasons:
it uses very precise temperature staging/measuring and any substance on the casing is going to throw off the thermal mass by ‘X’ amount… https://www.bosch-sensortec.com/media/boschsensortec/downloads/datasheets/bst-bme688-ds000.pdf - however, it’s unclear if this would be enough to significantly affect your readings or not
If some substance does touch the casing, it may give off VOCs or other chemicals that affect the readings as well
I do believe cleaning the surface with alcohol should be fine…but I would not allow any cleaner to travel into that casing’s tiny hole
If you do end up coating/testing (the main thing is I’d stay a good 0.5mm away from the casing, if possible)
please update/post results here!
Thanks Russell. I’ll give it a try and post the results. I mean, if I DON’T protect it somehow, there’s a fair probability it’ll be dead in a year anyhow, so if I’m out $25 by trying to protect it, it’s not the end of the world. 
That being said, do you happen to know how this device is protected during shipping / assembly / soldering? Does it come with some kind of plastic film on the casing, or a ceramic cap, or anything like that? I may be over-thinking this, but since the documentation advises not even TOUCHING it, I’m definitely curious if there’s an “acceptable” way to protect this during handling and installation.
Thanks!
You have a good handle on the situation! They ship in an anti-srayic bag; you xan just use nitrile gloves or similar would be fine 
