There are two fundamental issues with the cheap chinese diesel heaters:
They are not designed for this application. ………
A heat generator is a heat generator.
I feel the same heat from one of these units regardless of whether or not it is mounted in a motorhome, boat, truck or building. I would be at just the same level of risk of CO poisoning, fire etc. when inhabiting a space heated by one of these devices either in my motorhome or in my garage – as I don't sleep in a space heated by one when in the garage like I did in the van, possibly at higher risk when using the heater for it's "intended" use ?.
I chose to heat my garage with one after experiencing similar units fitted in 2 French built motorhomes that used them for space heating. One of these installations was reliable & offered well distributed heat throughout the 6.7 metre van. The other was unreliable & the van suffered from a cold bathroom, yet both were the ostensibly the same model of van from the same French builder & used the same Webasto Evo 55 heater – quality of installation made the difference. You would have thought a motorhome manufacturer building thousands of vehicles a year using the same heaters would be able to get this right but, sadly (and expensively, as I sold that van on account of the poor heating system performance ) this was not the case.
A 2KW fan or convector heater makes little impression on my double garage / workshop & the way it is wired I can't use more electrical heating capacity. Being a detached building , I can't put radiators in run from the house CH, which probably doesn't have the extra capacity required anyway. I did try a Clarke "Little Devil" propane torpedo heater that I inherited from my father (which he used to heat his garage / workshop) once. Only once because, while it heated the space effectively, the condensation on my bikes was horrendous – direct combustion heaters put a lot of moisture into the atmosphere in addition to the combustion by products. I did consider at one time fitting a pot belly stove fuelled by scrounged wood, but installation of one compromises how I could layout the workshop & would probably be more of a fire risk than the diesel heater. An added complication now would be the requirement to use an Eco Design / Defra approved stove, so a lot more expense than the old pot belly units that Machine Mart used to sell + recycling pallets doesn't comply with the "ready to burn" fuel requirements either. Waste oil heaters are a no-no now also.
The indirect combustion diesel heaters offer an economical, workable solution to my particular issues. I am comfortable with my installation (steel frame heater mounting sat on a concrete floor, adjacent to a steel workbench, exhaust through a concrete wall, fuel drawn from a dip tube in a floor mounted tank away from the heater & only operated while I am in attendance). I would be happy to replace it if you could suggest something "approved" that I have overlooked ?
I have not come across any suggestion of a Chinese heater failing in a dangerous way or the heater itself (as opposed to the installation) being responsible for a fire. Indeed the opposite seems to be the case – plenty about on how these fail in such a way that they don't start or shut down having detected a fault.
Nigel B.