This International Standard specifies design requirements and general considerations for hot-air heating of wheelhouse windows on board seagoing merchant ships to prevent condensation or frost, when specified by the shipowner. This International Standard is based on an outdoor air temperature of — 20 °C and applies to all conditions except those encountered in extremely cold climates. The annex gives recommendations regarding the air jets. NOTES 1 For electrically heated glass panes, see ISO 3434, Shipbuilding — Heated glass panes for ships' windows. 2 Users of this International Standard should note that, while observing the requirements of the Standard, they should at the same time ensure compliance with such statutory requirements, rules and regulations as may be applicable to the individual ship concerned.