Home Improvement : Too-Hot Bulb Can Cause Fire
One of the most underpublicized home safety concerns is the use of overly hot light bulbs to get extra light in fixtures not designed to handle the heat.
Very few homeowners understand that the wattage rating labels in light fixtures should be taken seriously. Failure to do so can result in damage to the fixture and/or insulation on the electrical supply wires. This can result in an electric shock or fire.
Ceiling light fixtures are especially vulnerable to overheating because heat rises, posing a risk even at relatively low bulb watt-ages.
If you are unsure of the safe wattage limit in a ceiling fixture or in any fixture where the bulb is either horizontal or inverted, do not exceed 75 watts.
Wall light fixtures and shaded lamps where the bulb sits straight up are not quite as likely to present a danger, but care should be taken to keep from burning the lamp shade.
In general, unless the lamp is marked otherwise, do not exceed 100 watts if the lampshade comes to within 10 to 12 inches of the bulb.
Beyond 10 to 12 inches of clearance, it is OK to go up to any comfortable wattage, but keep in mind that 150 watts generally serves the purpose while keeping operating cost and room heat to a minimum.