Do not recall checking a snow dam on the SA330J as they were fitted with a snow shield in front of the engine intakes, however on the AS332L snow accumulation in front of the air intake is a well known hazard after the double engine failure at Aberdeen on take-off due to a prolonged ground running/taxying in heavy snow.
If memory serves me right we originally had only one proximity switch to activate the cowls warning light on the AS332L, which would only operate if the dog house cowling was open (or missing - had one of those fly off before the mirrors were retrofitted) or the engine cowling on that side was open. Recall the late Ron Miles being told by Aberdeen ATC
'Do you know your engine cowling is open' on short finals in the early 1980s, that being the engine cowling with no proximity switch originally. And the mirrors had not been retrofitted before G-TIGD's tail rotor failure.
On the S92A we have no mirrors as the ice formed on them would affect the current icing clearance when it falls off into the engine intake, so it was fortunate that we had another aircraft taxying out behind us when our No.2 engine cowling fully opened prior to take-off.
Mirrors are thus very useful. Otherwise how do you check for signs of fire following an engine fire warning!