Are Flashlights Safe Around Gasoline?

Gasoline fumes can potentially be ignited by a spark at very low temperatures, especially if they are allowed to accumulate in an enclosed area. For a flashlight to ignite gasoline, it would need to malfunction and create a significant spark.

Properties of Gasoline

A "flash point" is the lowest temperature at which a chemical will produce enough fumes to be ignited by a spark or small flame. The flash point of gasoline is very low: -45 degrees Fahrenheit. The danger is reduced in well-ventilated areas. Ignition can occur without a spark at or above the "auto-ignition temperature," which is 536 degrees Fahrenheit for gasoline.

Flashlights and Sparks

For a flashlight to ignite gasoline, the batteries would have to create a spark. This may be possible with a seriously defective battery or flashlight, but it's unlikely with a working flashlight. The gasoline fumes would also need to have seeped into the flashlight's battery compartment.

Broken Bulbs

A flashlight using an incandescent bulb (as opposed to an LED) could potentially ignite gasoline if it were to shatter in an area with concentrated fumes. The tungsten filament inside a lightbulb can reach upwards of 4,500 to 5,500 degrees Fahrenheit. Bulbs are airtight, however, so ignition could only occur if the bulb were to shatter close enough to the gasoline to make contact with the fumes before cooling down.

References

• Engineering Toolbox: Fuels and chemicals: auto-ignition temperatures
• Engineering Toolbox: Flash point - fuels
• The Physics Factbook: Temperature of an incandescent light bulb