I have a Kozyworld wall mounted ventless propane heater. Whenever it automatically turns ON or OFF you get a strong odor of propane. While it is ON you don't smell propane. What is wrong with it. I have had it for four years.

It is possible to convert a natural gas ventless wall heater to propane, but it is not recommended. This type of conversion requires a significant amount of technical knowledge and expertise, and it is best to leave it to a professional. Additionally, the Charmglow Blue Flame CGN200TB model is not designed to be converted to propane, so even if you have the technical know-how, it may not be possible. It is important to check with the manufacturer and/or a professional before attempting any conversion.

good thing that you turned it off as it is now not operating as designed and that makes gas dangerous
call an accredited gas fitter to properly diagnosed the problem and repair/ replace it

It depends on what it smells like. Initially, when the unit is installed it should be burned on HIGH for 45 minutes to an hour. Doings that, burns off all the oils and seasons the heater. Sort of like seasoning a cast iron skillet. After that, the newness odors should be gone. It's normal to get a whiff of gas when the burner lights or turns off. It should dissipate rather quickly.

Although Vent-free (ventless) heaters are very safe to use and are 99.5% efficient, their one drawback is that pick up strong household odors, like strong cleaning products, carpet shampoos, new paint or stain odors, strong cooking odors, etc and make them worse. That's why it's always best not to use the heater during or after painting, for at least 2 weeks. Although your nose may not detect the paint odor, the heater can and will make it worse. Also, always use your range's exhaust hood when cooking. Hopefully, it's the vented type and not one of do nothing recycling hoods.

Also, thoroughly cleaning the heater inside and out , at least once a season, will go along way in reducing odors and maintaining the longevity of your heater.

One other caution, do not burn scented candles and operate the heater at the same time. Scented candles soot anyway, but adding the warm moist, comfortable heat from the vent-free heater, will cause them to soot 50 times worse. Trust me, it's not the heater, it's the scented candles sooting.

Hope this helped explain some of the things that you asked about and more. If I can be of further help, please ask me through the Leave a Comment link.

strong oder of what fumes or propane?

Blow the thermocouple out with an air compressor while the unit is off. Another way to clean it is with a CO2 BB gun. Make sure it's not loaded! lol!

You wont hear gas coming through until you depress the control knob. Otherwise try another tank. The ball valve may be stuck in the one you're using.

A can of air, vacuum and a long thin brush. Blow out any debris in burners and at the pilot assembly while running the vac. Brush all parts you can get too. Unscrew the pilot line from gas valve and blow in tube with can of air. Fire up heater and check for CO.

The propane may have a higher sulfur content; however, the odor may go away soon. It is probably caused by the dust and oxidation (micro-rust) that attached itself to every part of the heater while in storage, even though it was "sealed".

make sure you have the gas valve knob on turned to pilot while pressing that down while pushing the spark it should light or it is tripped on a safety like rollout switch or oxygen depletion sensor if equipped which all ventless heaters are