Firetube boilers kill when punctured, as there is a huge volume under pressure.The problem is the pressurized steam, not the fuel. There's a good reason why in rail locomotives the cab is usually as far away from the pressurized bits as reasonable.
Steam tractors for hauling artillery were regularly used so no issue there, but you never want to have one somewhere it might get shot, the resulting steam explosion might do more harm than the shell that opened it up might have.
Watertube boilers, has enough to pressurize the valve gear, lines and cylinders and not much more.
That why flash boilers were the choice for most steam vehicles that weren't on rails. Faster time from cold to power out was the main reason, safety#2