The invention relates to the field of controlled cooling of hot plate or strip shaped metal. An apparatus for the controlled cooling and a control method is proposed. The apparatus comprises a header fitted with a first valve (7), whereas the valves (7) allows air to escape from the header and prevent cooling fluid to escape from the header (1) when being filled and prevent air from getting back into the header. During operation due to the apparatus an improved operation even at low flow rates is possible.