In an office at a drilling location a portable electric heater was switched on by a mud engineer. After two minutes the mud engineer noticed smoke coming out from the heater while at the same time the smoke alarm went off. He switched off the heater immediately. However a small fire had already developed in the heater enclosure. The fire was put out with a dry chemical fire extinguisher. The upper part of the heater was destroyed (melted down) and scorch marks were evident on the wall (please note that same thing happened on another Rig two weeks later)