When we see people ask about safety of these, it often turns to "I'm leaving mine outside" and blowing the heat in. There is no advantage to keeping the unit outside and ducting the heat in at all. In fact, it has a lot of disadvantages for a rigid install like a camper. Fine for a tent, but not for a more rigid environment.
People often think they are "safer" if they are completely outside, but the truth is if there is a combustion chamber failure, bad fumes will still come thru the heated air tube. This is no different than a failure of any home furnace. The only difference so far then is your home furnace is UL approved (which carries a little assurance I suppose), whereas the imported heaters... well, I don't think even these days any of them are "Approved" by any entity. If you use them in a home or home shop and the place burns down, I bet the insurance fellers are going to try to avoid paying out. This however is about trailers and or campers.
In a trailer, it is best mounted exactly like they intend, thru the floor(or the wall if it is the only option). When mounted as designed, the exhaust system is effectively, completely outside. So is the fuel inlet configuration, so if you have a broken or leaky line, that too is dripping outside and not getting into the trailer. Making sure the exhaust tubing is sealed and directed away from any place exhaust could get back inside is important. CO, Oxygen and Smoke alarms are a must have no matter what the heat source is.
However, keep the TANK external. Spilled diesel STINKS inside any living quarters. It's not a semi truck or a farm tractor and shouldn't smell like one. That smell is almost impossible to get rid of when spilled inside anything.
Are they Safe ? I say yes. My first unit was an Eberspacher some 35 years ago. Now, I have used 4 of these imported ones in various applications and am not very worried... certainly not for a trailer or camper application, and especially not when you have the proper sensors you should have installed regardless.
The great news is they sure are cheap. My first one was well over $1500. Now, peanuts in comparison. They are without doubt, the biggest bang for the buck when it comes to heating a trailer... well, they were at least when fuel wasn't $6 per gallon. It was like a $1.20 when I had my first one and that meant it costed me no more than $1.20 per day to heat my rig. When I buy one, I buy 2. They are imported you know, and they have quite a few different controllers. Having a spare provides redundancy which gets really important if the heat is CRUCIAL to you. You must know that if it is going to quit working, it will be when you are actually using it just like a cordless drill.
I'm a big fan of redundant systems so maybe just have 2 smoke and CO detectors at each end of the trailer will alleviate my anxiety.....
