Please, if you must use a clamp on heat lamp inside a barn,
put a chain on the lamp near the clamp and attach it to
the wall or rafter so that if the lamp should be knocked
loose of the clamp, it won't be able to fall into the bedding
and start a fire. I have heard of three barns lost as a
result of a heat lamp falling into bedding and starting a fire.
I would worry that any clamp-on type of heat lamp has the potential of being loosened/knocked down (especially by *inquiring* type horses, like mine).
Our heat lamps are hard-wired (the same as our regular lights - all installed by the electrician when we built our barn). In fact, the heat lamps have their own *on/off* switch box located on the wall (above the switch box for the regular lights). The heat lamps are only in our foaling stall and haven't been used in years. I keep a piece of duct tape over the heat lamp wall switch (as a precaution against anyone accidentally turning them on).
As others have mentioned, the fire hazard with heat lamps is very real - you just can't be too careful.
Very good point Claddagh and Robin@DHH. I too have them secured against being knocked off. Those lamps put off an incredible amount of heat, where ever you put them make sure the animals cannot reach them, they will get burned.