Black Beetles Found in Furnace: Likely Click Beetles, Harmless

During air duct cleaning, a technician found black bugs behind a furnace face plate. They appeared dead but moved when touched. The homeowner sanitized the system but later found one on the floor and asks if they're dangerous.

Expert Answer: The blurry image suggests a click beetle (Elateridae), which are not typically found indoors. They are harmless and no treatment is needed. For a definitive ID, collect a few specimens and take them to your county Cooperative Extension office (find yours at extension.org) or a university lab like UC Davis/UC Riverside.

— Jack DeAngelis