Software design features: practical. . . 

pocketDP does the following design calculations:

• Staircase Pressurisation to Singapore Standard SS 553, formerly CP 13 (in-line with Australia Standard AS 1668.1).

• Door-opening force calculation to ASHRAE guideline.

• Differential Pressurisation, Airflow & Leakage Area calculations for room pressurisation conditions.

• Louvre sizing.

• in SI units only.

• Results can be saved to text file for editing & printing.

Staircase Pressurisation Design Criteria to SS 553  

The Staircase Pressurisation calculation is based on the following design criteria:

a) Airflow velocity of not less than 1 m/s through doors when all 3 doors are open (1 main exit door + 2 consecutive floors).

b) Minimum Pressure Differential between staircase & adjacent accommodation space is 50 Pa when all doors are closed. Unlike BS EN 12101-6 (old BS5588-4), there is no pressure differential requirement when doors are in open conditions.

c) Maximum Force required to open any door at the door handle shall not exceed 110 N.

To determine the air flow required to maintain a specified pressure differential, the following equation is used:

Q = 0.827 A (ΔP)1/2

Q = Air Flow rate (m3/s)

A = Flow area or leakage area (m2)

ΔP = Pressure difference (Pa)

To determine the door-opening force, the following equation is used:

where

F = Total door-opening force (N)

Fr= Force to overcome the door closer and other friction (N)

A = Door area (m2)

d = Distance from doorknob to the knob side of the door (m)

K = Coefficient (=1.0)

W = Door width (m)

ΔP = Pressure difference across the door (Pa)

Room Pressurisation and Differential Pressure 

Airflow through a large intentional opening is based on the Bernouli equation with steady, incompressible flow. General form that includes stack, wind and mechanical ventilation pressures across the opening is

where

Q = airflow rate (offset or differential airflow), m3/s

C = discharge coefficient for opening, dimensionless

A = area of opening (leakage), m2

dP = pressure difference across opening, Pa

Note: standard air density is used in the above formula.

A room's differential pressurization value with respect to an adjacent area is totally dependent upon the room's differential airflow and its leakage area. The +ve or -ve pressurization relationship between spaces establishes the potential for directional airflow. Therefore, there must be an opening (typically clearance openings or gaps around doors, and unintentional construction gaps) between the spaces for airflow to actually occur. The desired pressure relationship between rooms or spaces is created and maintained by a properly designed and controlled ventilation system to achieve a specific airflow offset as determined. For example, to maintain a room at a -ve pressure with respect to the adjacent space, the required airflow offset will cause air from the adjacent space to flow into the room through the defined leakage area.

Example: Staircase Pressurisation calculation for a 10-storey building 

The following calculation is done using pocketDP program.