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Hospitals are sophisticated environments that require special HVAC system design, maintenance and repair considerations. HVACs are accountable for balancing indoor air quality and providing a safe temperature for patients and staff. B Gautham Baliga, Opal HVAC Engineers Pvt. Ltd, expresses the importance and running of HVAC systems in the healthcare facilities.


Hospitals need a utilitarian HVAC system to stay viable. This is notably true for places like a clean room or an operating room. Air-exchange, humidity, pressure and temperature have to be accurate in such environments to minimize the risk of infection for patients. However, even outside the operating room, HVAC systems are required to not only keep high indoor air quality levels but also maintain specific temperatures to minimize bacterial growth throughout the hospital. A well-maintained HVAC system can help reduce operating costs in addition to providing a safe environment.

What is an intelligent air conditioning system and the practices thereof which can ensure prevention of spread of infection?

HVAC systems in healthcare facilities are for patients, healthcare workers & visitors and all should remain safe in the environment. The HVAC systems are in support of patients who are uniquely vulnerable to elevated risks of health, fire and safety hazard. Healthcare facilities vary widely in the nature and complexity of services provided for injury or degree of illness of patients.

With the advent of superior control systems, it is possible to implement the various needs and also not guzzle energy. Take the example of an operation theatre meant for heart operations. The environmental requirement is of operating at low temperature and then as required, fast reheat. This is possible with appropriate designs and controls. Further, the aircon system is not to be shut off during non-use hours as pressure gradients, which are imperative for infection control, have to be maintained at all times. So, we have what is called the ‘idle mode’ or ‘night mode’ operation. During this mode, the air handling fan motor speed is reduced and room temperature elevated. At the same time, pressure gradient is not compromised. This way energy consumption during idle mode can be as low as 20% of the normal energy.

This is just an example of what can be done to make aircon systems intelligent.

What are the present practices & challenges?

Though air-conditioning systems have become sophisticated, the underlying requirement is maintaining equipment clean. This activity of cleaning is unfortunately given a short shift in most hospitals.

Take the case of filters. Filters will protect from dust & micro-organisms. Pollutants will accumulate in the filters and some of them could act as nutrient substrate for micro-organisms. Filters thus require careful cleaning at regular intervals. Filter cleaning can be hazardous to the technicians & they need to be trained to perform this activity with proper PPE (personnel protective equipment). This activity is contracted out in most hospitals and the work is carried out by temporary, untrained and unsupervised personnel.

The AHU condensate pans are growth centers for bacteria and are mostly ignored in regular maintenance. In many cases, there is water logging in the pans because the drains are not well constructed and consequently there is mold formation. Routinely attending to this detail can improve air quality substantially.

Air intakes are accumulation sites for dirt and debris, including rotting botanical materials like leaves, which are growth sites for fungi such as Aspergillus fumigatus and thus require routine cleaning.

Control systems and electronic annunciation can indicate when the filters are choked, can help maintain pressure gradients, temperature and humidity. Even though the costs of control systems have dropped considerably, most hospitals have not adopted them. This could be because of ignorance of what these can achieve. Thus, most of the actions for controls are with human intervention and these can be tardy most of the times.

What are the mistakes with regards to temperature control that could lead to mismanagement/ spread of infection?

It has been medically proved that conditioned spaces need to be maintained between 40% and 60% relative humidity (RH) for the wellbeing of the occupants. In most cases, RH is neither maintained nor controlled.

Rooms where RH exceeds 70% for prolonged periods are likely to experience airborne fungi and house dust mites.

Each mold has its special growth characteristics. Once it has started to grow, it is difficult to stop by lowering humidity because one of the metabolic products of growth is water which then allows growth in drier conditions.

Condensation should be avoided on building surfaces as this supports mold growth. One has to only rip open the plaster on external walls of hospitals in humid areas such as Mumbai to understand the extent of the malaise.

What are the other air conditioning systems suitable for small, medium & large size hospital?

Today, we are spoilt for choices in terms of available air conditioning systems. The small and medium hospitals will have to look at unitary systems, condensing units and VRF systems and the big hospitals will have to look at centralized chillers.

Having stated this, we have to understand that the ubiquitous room air conditioners and Hi wall and cassette units are at best used only in certain type of patient rooms, consulting rooms and office/admin areas. These are prescribed for ICUs, OTs and other critical areas though they are mindlessly used in such areas

The underlying consideration for air conditioning indoor units and AHUs [air handling units] is serviceability and ease of cleaning of filters and other parts.

Energy consumption is main worry of hospital authorities where Air- Conditioning is concerned.

Energy is a cause of concern for all hospitals and air conditioning consumes a huge chunk of the energy.

It will be a passé to mention that we should invest in energy efficient equipment.

What goes unnoticed is that a significant energy is lost because of leaking ducts and poor insulation due in great part to improper commissioning and TAB [testing and balancing] process- these measures have an energy saving potential as high as 20~25%!

To reduce energy consumption, it is a common practice to reduce fresh air intake and increase chilled water temperature. Both these measures are retrograde. They adversely affect infection and RH.

The legitimate ways of reducing energy is to install energy recovery systems for RH control, have idle mode operation for areas, proper system design, energy efficient equipment and a tightly built civil infrastructure.

At the end of it all, it is all about people- the professionals handling the systems from the inception, design, installation and maintenance. All need to be sensitized to the special requirements of healthcare facilities.

ISHRAE (Indian Society of Heating, Refrigerating and Air Conditioning Engineers) has already been into certifying HVAC Design and Service professionals, Draughts men and Cleanroom professionals. This year, the Society has taken up the onerous task of developing certification for Healthcare HVAC professionals and a TC (technical committee) has been instituted for drawing upon the skills and knowledge of micro biologists, doctors, healthcare workers and engineers to help in this process. Having certified professionals in the field will assure the users that their complex air conditioning systems are in good hands.

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