Which electrical devices are commonly known as arcing ignition sources?

Arcing ignition sources are devices that can create electrical arcs as a result of their operation, which can ignite flammable gases or vapors. Thermostats and garage door openers are commonly associated with such arcing phenomena due to their electrical components and the potential for circuit interruptions or mismatches. These devices often involve mechanical contacts that can create sparks during operation, especially when turning on or off, which increases the risk of igniting any nearby combustible materials.

In contrast, while washing machines and refrigerators do utilize electricity, they typically do not create arcing in the same manner due to their design and operational characteristics. Similarly, smoke alarms and air purifiers are designed to prevent hazards and reduce the risk of fire, which makes them unlikely candidates for being ignition sources. Lastly, TVs and microwaves, though they contain electrical components, do not usually create significant arcing that poses ignition risks in the context of gas piping safety. Therefore, thermostats and garage door openers are correctly identified as the devices that can be considered arcing ignition sources.