incendiary device; ignition device
Refers to a device designed to start a fire or cause ignition, often in military, industrial, or safety contexts.
The incendiary device is activated by remote control.
The firefighters found a suspicious ignition device.
着火装置 is a more general term for any ignition or lighting device, while 発火装置 often implies a device that starts a fire, sometimes with a destructive or military nuance.
Compound of 発火 (はっか, 'ignition') and 装置 (そうち, 'device').