So I um, kinda bought a heater...!

It really is cool. With proper ventilation and a CO detector, should be fine. There really isn't much to inspect. Bench test it and see if it works.

Sort of... Bench test: On a shop bench or other safe area, connect a regulated propane source (has a regulator). Leaving the heater off, sniff for propane. If no odor, you can light it. You shouldn't need a CO detector in an open area. You just want to see if it glows or burns, whatever it's supposed to do...

Hook it up and let it burn for a while to see how hot it gets, some of that type of heaters had be be kept a certain distance from combustible surfaces. Some as much as two feet away. while it is burning place a few pieces of plywood around the back and sides about the distance that you are thinking of placing from the mounting place in your trailer then burn it on highest setting for a couple of hours to see how hot the plywood gets. An O2 sensor system could be added but I believe it will require a pilot light and a thermocouple to make it work and most of those older heaters just had a valve you turned on and lit them with a match. I would also suggest installing a co2 alarm in the trailer as many heaters of yesteryear didn't burn clean as modern vent-less heaters and they are bad enough. you will also notice a smell as the propane burns inside a small trailer most likely. It really looks cool if it will work safely.

I will let you know what happens. I was doing some reading on "ventless heaters" last night and there are safety issues that must be carefully attended to. I will be investing the money to make this work safely. I want to find out if it would be logical to have a vent pipe that exits outside the trailer. Kind of a natural flu. I am thinking to create a steel lined place at the front bottom of my closet with some steel like the heater in the photo, then have an opening above the heater vent the flue to the outside... possibilities, possibilities..

And check the connections with soapy water after you connect the propane but before you turn the valves on to light it. Put soapy water on it, if it bubbles, it leaks. You should do this with your fittings when you install it, too.