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HVAC System Design for Multi-Specialty Hospital

Hospital air conditioning is always considered as high sensitive issue while planning with other services. Recently completed healthcare project by the author is a multi-specialty hospital located in new Mumbai, where two aspects were very important. One is the high end HVAC system required for healthcare and second is the height restriction in between false ceiling and slab to run all services.  Another challenge came while crossing the ducts and pipes within the beams. Care has been taken to provide all modern facilities available either in Apollo or Seven Hills or so on in this type of hospitals where construction area is nearly 50,000 square feet.

Various aspects need to be discussed in planning stage itself which will help in smooth execution.

  • The need to restrict air movement within and between various rooms especially when operations carried out. Air lock of as small as 20 square feet has provided with positive pressure difference from adjacent rooms. This pressure difference achieved though control of fresh air in all adjacent rooms.
  • The specific requirements for ventilation and filtration to dilute and remove contaminants in the form of airborne microorganisms, viruses, and odour. Separate fans with individual ducting have provided in these rooms so that there is no mix of air take place.
  • Different types of temperature and humidity requirements for various areas. It was not possible with only VRV system, when specialised dehumidifiers installed in different rooms to control the humidity.
  • Permit accurate control of environmental conditions through centralised VRV system.
  • Control of air quality and air movement through air handling units, fan coil units and Treated Fresh Air units.
  • Provide a healthy and lavish atmosphere to take care of high end client, especially when they are waiting for their turn to come.

While designing the different rooms of the hospitals, the design team has gone through various alterations of design to achieve the goal while not compromising the technical responsibility as a consultant.

Figure 1: Operation Room Ducting Layout

Control of infection sources and its measures in Operation Rooms

Infectious bacteria are transported by air. Droplet or infectious agents of 5 mm or less in size can remain airborne indefinitely. It has been shown that 90 to 95 per cent effective filters remove 99.9 per cent of all bacteria present in hospitals. Epidemiological evidence and other studies indicate that many of the airborne viruses that transmit infections are sub- micron in size, thus, there is no known method to effectively eliminate 100 per cent of the viable particles. HEPA filters or Ultra-Low Penetration (ULPA) filters provide the greatest efficiency currently available. Considering this, the isolation rooms with appropriate ventilation pressure relationships have provided to prevent the spread of airborne viruses in the hospital environment.

Use of Treated Fresh Air system in entire premises

Treated Fresh Air (TFA) has a major role to play in hospitals. Outdoor air in comparison to room air is virtually free of bacteria and viruses. Infection control problems frequently involve a bacterial or viral source within the hospital. Ventilation air dilutes the viral and bacterial contamination within the hospital. Properly designed, constructed and maintained ventilation systems preserve the correct pressure relationship between functional areas; they remove airborne infectious agents from hospital environment. Fresh air at a rate of 15 CFM per person have provided in all rooms and care has been taken that same amount of air get extracted through toilets fans all times so that there is a continuous air change in the premises.

Figure 2: NICU rooms with Section

Isolation Rooms( NICU)

There is one NICU room which has to be separated from other rooms. With the patients of harbour transmittable microorganisms helps in various modes of transmission to contaminate the environment creating the necessity to control infections. For this, there is a need to create the following special isolation rooms:

  • Standard Pressure Room for patients who require contact or droplet isolation is provided.
  • Negative Pressure Room for patients who require airborne droplet nuclei isolation to reduce transmission of disease via the airborne route (Class-N) is provided.
  • Requirement of separate exhaust system dedicated to NICU room, removing a quantity of air greater than that of the supply system have provided.
  • Directs the exhaust directly to outside also provided with by pass connection.
  • Positive Pressure Room with a positive pressure relative to the ambient pressure to isolate immuno compromised patients such as certain transplant and oncology patients have provided. The aim is to reduce the risk of airborne transmission of infection to susceptible patients (Class-P).

Isolation Room Pressures

Importance of Air Lock Function

  1. Provides a barrier against loss of pressurisation and against entry or exit of contaminated air in or out of the isolation room when the door to the air lock is opened.
  2. Provides a controlled environment in which protective garments can be donned without contamination before entry into the isolation room.
  3. Provides a controlled environment in which equipment and supplies can be transferred from isolation room without contaminating the surrounding areas.

Humidity Control

Bacteriological microorganisms ride on dust particles. Its attract ability to one another is favoured by low relative humidity resulting in increased static energy. High humidity in the hospital enhances the danger of growth of Pseudomonas aeruginosa. Humidity in operation room is believed to contribute to the prevention of dehydration of exposed tissue. At relative humidity of about 50 per cent, a very thin invisible film of moisture forms on the operation equipment and other surfaces. This film of moisture conducts static electricity to earth before a spark producing potential is built up. To minimise the explosion risk, the relative humidity required is 40-65 per cent. VRV Indoor Units have installed with RH indication in the remote controls have provided along with few portable time dehumidifiers.

Conclusion

The entire design team has tried to take care of all minute aspects with support from doctors’ team to provide maximum facilities in minimum space available.