Manual fire alarm boxes consist of both single and double-action device
A single-action device requires the user to do only one thing, which most often is to pull the handle down. Other single- action alarm initiating devices feature push buttons instead of the pull down handle
A double-action device requires the user to perform two actions before the device is activated. For this manual fire alarm box. the user must push in a small door. and then pull down the lever. NFPA 72 explicitly petunia both single-and double-action boxes. But does not require one or the other. However. your local building. fire or life safety code might specify one or the other.