The air flow can be adjusted steplessly according to the weather conditions and needs. Alternatively, the valve can be equipped with an automatic bimetal adjuster, in which case it adjusts to the outdoor temperature on its own. Air-In wall valves can be used in houses with mechanical or gravitational air vent systems. The Air-In wall valve is a quality product made of galvanised, powder coated steel.Courtesy by rakennustieto Finland. These downloadable objects are only available in Finnish at the moment.