Controlling LP Gas burner with microcontroller: flame sensor ideas needed
There are three common flame detectors used for fuel-gas heating systems: Flame Rectification, Temperature Sensing using a thermocouple, UV sensing.

UV sensors are not reliable when used outdoors unless the sensor and the flame pot are completely shielded from outside light.  One of the systems that I had to troubleshoot several years ago suffered from exactly that problem - worked when it was on the ground, didn't work when it was up in the air on a lighting truss.

Flame Rectification needs a high-voltage AC source, usually in the 160 Vac range.  Not difficult to generate but . . .

Another problem with Flame Rectification is when (not if) the flame-sensing rod becomes contaminated with combustion products from dirty fuel-gas.  Easily fixed with some steel wool or other abrasive pad but a maintenance hassle non-the-less.

Temperature Sensing is both inexpensive and reliable.  The only problem is ensuring that the thermocouple tip is always within the flame cone.

There are a lot of safety concerns if you are building this for a commercial application.  Certification is a hassle and is always expensive.  You would need to study the relevant regulations and design both your hardware and software to meet those regulations.  Pay particular attention to the requirement for fail-safe operation.