There is a very good reason Diesel engines are used in underground mines while gas engines are not. Diesels produce far less CO than gasoline engines. Diesels (compression engines) operate in a lean burn condition or high intake air volume as compared to petrol engines which operate in a near stoichermetic condition.
In underground mines an air testing device such as a Drager tester is a normal workday tool. In a freshly blasted rock heading a large ventilation fan will quickly evacuate blasting related nitrogen gases. The diesel trucks and loaders begin mucking out the broken rock. With adequate ventilation CO will begin to slowly rise, but not to a dangerous level. Then onto the next heading, all very safe.
No way would a gasoline powered loader work due to CO levels alone in an underground mine. Not to mention engine output, longevity and fuel efficiency.
A normal diesel exhaust will emit (at tailpipe) approximately 1500ppm or less CO whereas a gas engine will be in the 10,000 ppm range but climb to 60,000 when the accelerator is pushed down.
Catalytic converters change this situation. A finely tuned gas engine with fuel injection, turbos and catalytic converters can commonly achieve less than 100 ppm CO. But a normal inefficient small gas genset on a twin hulled houseboat (air trap for swimmers) has all too often proved deadly. Or likewise a chainsaw, lawnmower, outboard, leaf blower etc.
None of this is rocket science, just workplace conditions 101 for underground miners. Unfortunately for those contemplating suicide with a diesel in the garage, you'll get very sick rather than dead. Living a vegetable state life for a long time, or at best stuck reading TF forever.