Door leakage and door protection in Operating Theatre Suites
Door leakage across closed doors (based upon HTM 03-01 figures)
|Differential pressure - Pa|
|Hatch per lin. meter of 3mm gap||0.004||0.008||0.01||0.011||0.012||0.012||0.013|
The leakages shown above are based upon the following door sizes :
Single doors - 2.01m high x 0.8m wide with gaps of 3mm on the top and sides and 4mm on the bottom. Total gap 0.01766 m2
Double doors - 2.01m high x 1.8m wide with gaps of 3mm on the top and sides, 4mm on the bottom and 2mm between leaves. Total gap 0.02688 m2.
Where doors are of different sizes or their gaps are not as above use the following formula.
Leakage = 0.827 x area of gap in m2 x sq. rt. of the differential pressure in Pa
Door Protection volumes in m3/s
|Room Class||Door type||Dirty||Transitional||Clean||Sterile|
|0 or 0.28
0 or 0.57
|0 or 0.28
0 or 0.57
|0 or 0.28
0 or 0.28
Achieving Door Protection
The purpose of door protection is to provide a sweep of air across key open doorways to prevent, as far as possible the backflow of air from areas of lower cleanliness and thus the ingress of bacteria and other contaminants. Door protection volumes and velocities for standard Theatre layouts are indicated below.
|Door location||Room Classifications||Door
|Lay up Prep - Theatre||Sterile - Sterile||Single||0.28||0.175|
|Lay up Prep - C. Corridor||Sterile - Transitional||Single||0.39 *1||0.243|
|S.P.S. Prep - C. Corridor||Sterile - Transitional||Single||0.39||0.243|
|S.P.S. Prep - Theatre||Sterile - Sterile||Single||0 *2||0|
|Theatre - C. Corridor||Sterile - Transitional||Double||0.75||0.208|
|Theatre - Anaesthetic||Sterile - Clean||Double||0.57||0.158|
|Theatre - Disposal||Sterile - Dirty||Single||0.47||0.293|
|Scrub - C. Corridor||Sterile - Transitional||Single||0.39||0.243|
|Anaesthetic - C. Corridor||Clean - Transitional||Double||0.57||0.158|
|C. Corridor - Disposal||Transitional - Dirty||Single||0.28||0.175|
* These values are the minimum design values and in practice are exceeded in some cases.
*1 This volume is achieved by a supply of 0.34 m3/s in the Lay up, augmented by door leakage across the Theatre - Lay up door. This will be 0.06 m3/s as the pressure in the Lay up with the door to the Corridor open is 3 Pa.
*2 S.P.S Preps normally have a single door to the Theatre which is fitted with a door transfer grille. This should be sized to pass 0.23 m3/s when the Prep to Corridor door is open. Door leakage across the Prep - Theatre door will be 0.06 m3/s (single door @ 22 Pa) in this condition thus providing a total of 0.39 m3/s for door protection across the S. P. S. Prep to Corridor door.
There should be no door between Scrub and Theatre.
Double doors should be avoided between the Theatre and Disposal unless the nett inflow to the Theatre (supply plus inflow from Prep) is increased to at least 0.95 m3/s.
Protecting Individual Open Doors
- Lay-up Prep - Corridor Door Open
- Lay-up Prep - Theatre Door Open
- S.P.S Prep - Corridor Door Open
- Theatre - Anaesthetic Door Open
- Theatre - Exit Bay Door Open
- Scrub - Corridor Door Open
- Theatre - Disposal Door Open
- Anaesthetic - Corridor Door Open
- Clean Corridor - Disposal Door Open
- Disposal Corridor