[weberer]

In the US and other developed countries, they burn clean fuels like natural gas or propane. These emit minimal soot.

https://en.wikipedia.org/wiki/Clean_fuel#/media/File:Access_...

[fooblaster]

Unfortunately perhaps not as clean as you would hope: https://pmc.ncbi.nlm.nih.gov/articles/PMC9819315/#:~:text=5.....