washing up liquid round the connections see if it bubbles, really though these are no more dangerous than a bbq
In a way I agree with you when used correctly they are no more dangerous than a bbq, but every year people die from using bbqs in the wrong place like a in a tent. Outside a disposable bbqs carbon monoxide will be dispersed into the air but in a tent the carbon monoxide can build up.
These water heaters will require a minimum room size and are intended for short use only and not all day, add to that lack of proper maintenance and safety checks and they are risky.
Dave Willis has proved how easy it could be to miss a gas leak, when testing gas pipe i have seen situations where it failed and there was a leak but you could not smell gas and sometimes you will even struggle to find a leak with leak detection fluid.
People may mock me on here but that is due to their lack of knowledge meaning they fail to see the risks. But I guess "good old common sense"(eg it will be alright as long as I keep the doors open)is far more valuable than taking notice of regulations developed through knowledge and experience to prevent accidents happening.