Technical Booklet K Ventilation·Page 21·2.7
Rapid ventilation provision in habitable rooms
Each habitable room must be capable of extracting a minimum of four air changes per hour directly to outside, typically via openable windows or doors, or by mechanical extract system where windows/doors are not available.
Rapid ventilation provision is required in each habitable room and should be capable of extracting a minimum of four air changes per hour (ach) per room directly to outside. In normal circumstances, openable windows or doors can provide this function in accordance with Appendix B. However where they cannot, a mechanical extract system should be provided.
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