I got caught in my Focus on the interstate with a flat tire so I blew in a can of fix a flat, later had the tire removed from the rim for repair and the fix a flat is like water, sitting on the bottom. The low tire sensor didn't doesn't seem to mind the liquid. It's still working.

I will say that mine activate at 20 psi. And even after filling the tire back to 35 psi, the sensor takes like 1/4 to 1/2 mile to reset.