Method of making safe a heat treatment enclosure operating under a controlled atmosphere

A method for increasing the safety of a heat treatment enclosure operating with a gas atmosphere, the enclosure including a cooling chamber for rapidly cooling a metal strip running from an upstream chamber to a downstream chamber by means of a plurality of guide rollers, wherein the rapid cooling chamber is filled with a controlled atmosphere of high hydrogen content, the method comprising the steps:

• providing a plurality of gas locks at an inlet an outlet of the rapid cooling chamber;
• providing at least one first pressure balancing duct between the inlet and outlet of the rapid cooling chamber;
• and
• providing a second pressure balancing duct between the upstream and downstream chambers;
• wherein the first and second ducts balance the gas atmospheres between the upstream, downstream, and rapid cooling chambers thereby controlling the flow rate of gas flowing through the gas locks.