Knok out locks (allso refered to as fume evacuation locks) are realized according to european regulations concerning safety against fire risk in pubblic buildings. European reagulatins require safety devices whose purpose is to evacuate combustion fumes by means of a self-acting or manual control.

Locks are usually closed, and open because of a termic reaction.

When the temperature of 72°C is reached the fuse yields causing the levering control system to be actioned by means of the termic release device.

Knokout locks are realized as follows:

- multiple bladed (sheet zinc tongued envelope)

- single bladed (sheet zinc envelope and plasterboard blade)

On demand 96 °C, 124 °C, 220 °C termic fuses are supplyed.