failure to replace burned out lamps in series-constructed miniature christmas light strings, or replacement with lamps of incorrect voltage rating, can lead to very high power dissipation by some or all of the lamps in the series string. hot spot surface temperatures as high as 470c were measured for lamps subjected to simulation of the above conditions. additional testing showed that contact with surface temperatures above 390c can cause glowing ignition, within two minutes, of cellulose material (e.g., tissue paper, decorative cotton) often found in the vicinity of christmas light strings, and can cause flaming ignition in some samples of absorbent, untreated cotton. furthermore, the hot spot surface temperature of normally operating lamps (no excessive power dissipation) can, particularly if the filament is off center, be higher than the melting temperature of some commonly used plastic insulating materials such as polyethylene contact between a hot lamp and insulating material can thus cause a shock hazard due to exposure of current carrying parts. light string design and performance requirements that would prevent these hazards are discussed in the report