The requirements of an air-conditioning system as laid down in BCAR’s
Please provide a link to your BCAR.
See House of Lords Science paper in 2000
House of Lords - Science and Technology - Fifth Report
See: 5.29
"There are no specific regulatory limits for cabin relative humidity."
"5.33 The definitive experimental work on this topic was carried out at the then RAF Institute of Aviation Medicine (now DERA) at Farnborough, Hampshire. This showed clearly that exposure to 5% RH for 24 hours did not lead to changes in overall water balance amounting to central dehydration (p 72). Professor Nicholson also showed that the maximum increase in water loss for a person spending 8 hours at 0% RH was about 0.1 litre, well below even the thirst sensation level[74]. He, Dr Sowood (p 72), and Professor Denison (p 94, Q 214) were of the firm view that any extra water loss due to the dry cabin environment is of no significance to health, and that central dehydration of passengers in low humidity aircraft cabins is a myth. As Dr Giangrande noted (p 234), the assertion in Q 108 that breathing dry cabin air means that passengers are not replenishing their blood plasma is nonsense."