Abstract: Hot coke 3 expelled from a coking chamber is conveyed in a quenching car 2 to a quenching tower 4 past an infra-red detector 6 which provides a signal to initiate supply of the quenching water. It is a problem to control the amount of quenching water supplied to achieve adequate quenching without adding excess humidity. To solve this, the detector produces an analogue signal dependent on the surface temperature of the passing coke, and the duration of supply of quenching water is determined from this signal. The signal may also be used to control variation of the degree of quenching at different parts of the car and also to control the heating of the coking chamber.