Page 48 - policy and procedure infection control

Policies and Procedures on Infection Control

3.5 Design of Isolation Rooms

Patients who need airborne isolation should be placed in well ventilated areas with a directional
airflow from health care worker to the patient. Adequate ventilation is commonly defined by air
exchange rate. It is desirable to achieve > 12 air change rates per hour (ACH). The air should
flow from corridors (cleaner areas) into isolation rooms (less clean areas) to prevent spread of
contaminants to other areas.

3.5.1 Ventilation
This can be achieved by three possible strategies,
1. Natural ventilation
This may be an option provided the isolation areas are away from other parts of the
hospital, and are built in places predicted to have good prevailing winds year round.

The air should be directed from patient caring areas to outside open areas not regularly
used for transit of persons.
Inside the airborne precaution room, the patient should be placed near the exterior
wall, close to open window(s), instead of close to the inner wall.
2. Use of exhaust fans
In places where natural ventilation is not suitable, and fully mechanically-ventilated
airborne precaution rooms cannot be installed due to limited resources, the use of
exhaust fans (with adequate pre-testing and planning) may help to increase ACH
rates and generate negative pressure in the rooms.
The fans should be installed on exterior wall(s) where room air can be exhausted
directly to the outdoor environment free of transit of persons.
The size and number of exhaust fans needed depend on the targeted ACH, which
must be measured and tested before use. The position of exhaust fans with relation
to doors and windows should be carefully planned to avoid short circuiting.
3. Use of mechanical ventilation
The engineering requirements for a mechanically ventilated negative pressure rooms
are as follows,
• Negative pressure (greater exhaust than supply air volume);

• Pressure differential of 2.5 Pa (0.01-in. water gauge);
• Air flow volume differential >125-cfm exhaust versus supply;
• Well sealed room, approximately 0.5-sq. ft. leakage;

Ministry of Health Malaysia 37