View Full Version : negative pressure ward for hospital

02-09-2003, 04:43 PM
My company is having a job in Hong Kong, which previously had a big virus SARS, so need to convert the normal ward to a negative pressure ward.

By means of extract more air than the supply air, can anyone help me how to carry out the commissioning process, will there be CIBSE commissioning guide to follow?

02-09-2003, 09:01 PM
Hi Watana

Air balancing is easy but you need the right gear to do it. Air velocities from each grille must be measured and converted into volume flow then added together to reach a total air input or extract from the space.

If you require a positive airflow then you should be looking for at least 10% more air in than out. If you require a negative flow then it is the other way around. You can of course design for more than 10% but this is dependant on the application.

Do you know how to convert velocity into volume flow?

04-09-2003, 09:10 PM
Watana, CIBSE Code A should cover your commissioning process but would suggest that the design consultant should specify the commissioning requirements.

Maintaining differential pressures across rooms does require some careful design and commissioning.

Considering the medical aspect put as much responsibility onto the designer as you possibly can.

Good luck with it.

14-09-2003, 03:56 AM
thank you for your assistance.

I know how to convert the velocity to air flow volume by multiply the velocity by area of grille.

12-03-2005, 04:31 PM
at last, I have finally finished 2 separate jobs of negative pressure ward, some with an ante room & main bedroom.We need 10 Pa differential between ward & corridor.

My working experience is you must do a first class workmanship air duct and test the leakage of air duct, according to DW144, it is better to test the air duct with the air duct branch duct attached, seal up with plastic bags. both supply & exhaust need to be tested. Minor leakage will not maintain the differential pressure, and the sealing of the wall openig & gaps between ward need very special attention, minor leakage will not get the ideal negative pressure, also our government spend a lot of money to those wards

13-03-2005, 10:44 PM
Well done Watana, yes leak testing of the ductwork is most important when you are attempting pressure differentials across rooms.

Also, thank you for giving us an update on this thread.:)