The primary role of a Health Care Facilities (HCFs) is to provide effective medical treatment and nursing care to the patients. Recently, Indoor Air Quality (IAQ) has become a significant issue in the hospital settings in urban and rural areas in India. The various departments in healthcare facilities include operating theatres, intensive care units (ICUs), inpatient wards, outpatient departments (OPDs), pharmacies, radiology departments and laboratories. Each department has its specific functions which differ in their day to day functioning from other facilities. IAQ of a healthcare facility involves multiple factors such as thermal comfort (temperature and humidity), concentration of airborne particles, chemical contaminants, outdoor air quality which affect the exposure and wellbeing of the patients. Poor hospital IAQ can result in various severe and acute building related illnesses, ranging from minor headache, fatigue, eye and skin irritation to respiratory and cardiovascular diseases and eventually premature mortality. In hospitals, the occupants primarily exposed to poor IAQ are patients, healthcare workers, and visitors.

Occupant diversity in healthcare facilities has made hospital environment more complex than any other commercial building. Maintaining a good IAQ is the mandatory requirement for any healthcare facility. Good IAQ safeguards the patients, hospital staffs and visitors from the hospital acquired infections (HAI) and sick hospital syndrome (SHS).

As per World Health Organization (WHO), at any given time over 1.4 million people across the globe suffer from hospital acquired infections (HAI). Hospital acquired infections (HAI) prevalence is higher in the Intensive Care Units (ICUs) than other areas of the hospital. As per a study by International Society of the Built Environment (2008) on indoor and outdoor air quality in hospitals, it was estimated that bacterial counts in ICUs, orthopedic wards, neonatal wards, dialysis wards and post operative wards were found to be beyond the recommended levels. Poor IAQ in hospitals may also be related to Sick Hospital Syndrome (SHS) in its micro-environment. SHS may result in acute discomfort, dizziness, eye, nose, skin and throat irritation amongst the exposed population. In many ways, SHS is linked to the efficiency of hospital ventilation and performance of air conditioning system in the micro environment. Achieving good hospital IAQ is a humongous challenge to the hospital engineers, planners and hospital workers. IAQ can be improved and maintained when engineers, architects and the hospital staff have an innate understanding of the various components affecting the indoor environment.

Indoor Air Quality (IAQ) in a hospital setting primarily depends on these five major factors of exposure: patients, staff, visitors, building and the outdoor environment. By looking at each of these components, architects or engineers can develop a sound methodology that can help in improving the IAQ. Visitors and hospital staff are always more prone to catching infections from the patient. If air quality is not maintained and certain hygiene practices are not followed within the hospital premises, then risk of spreading contaminants increases by manifolds.

Indoor Air Pollutants in Hospitals

The indoor environment in HCFs contains a variety of particles and gaseous contaminants such as carbon dioxide (CO2), Carbon Monoxide (CO), Formaldehyde (CH2O), Total Volatile Organic Compounds (TVOCs), Respirable Suspended Particulates (RSP), Radon (Rn), Glutaraldehyde (C5H8O2), Nitrous Oxide (N2O), latex allergens, and total bacterial count. These contaminants are commonly referred to as indoor air pollutants in the healthcare facilities.

Determinants of IAQ in hospitals

In healthcare facilities, IAQ determinants falls into four major categories: patients, staff, indoor environment within the hospitals, and the outdoor environment.

If an active TB patient coughs or sneezes, it exposes the other patients or staff or visitors to infectious microbes which can trigger respiratory illness in healthy individuals. Patients are a major source for contaminating the indoor air and are the main reason to improve the Indoor Air Quality (IAQ). Patients at these facilities are suffering and being treated for different health concerns. Patient coughing can introduce contaminants into the air and onto adjacent surfaces. Bodily fluids as a result of wounds, infections, incontinence can be transferred from the patient to clothing, bedding, and other surfaces. Odour is also a big problem in hospitals due to wounds, infections, diseases, medicines and various medical procedures.

If certain procedures and hygiene practices are not followed by the hospital staff, then there is a potential risk of spreading contaminants generated within the hospital by patient and other factors. Chemicals used to disinfect medical equipment such as glutaraldehyde and ethylene oxide (carcinogenic) which contribute significantly to IAQ problems. There are standards which define the acceptable limits of IAQ but some population may show reactions to even smaller concentrations. In addition to the patient- borne illnesses, indoor environment within the healthcare facilities is one of the most common sources of airborne pollutants. Chemicals used to clean and disinfect the indoor environment in hospitals are the major source of airborne pollutants. Outdoor air could possibly be the major source for indoor air pollutant concentration. Several factors including vehicular emission, industrial emission, crop burning, wind speed, wind direction and emission from various building can contribute to the high pollutant concentration in outdoor air

Factors Effecting IAQ in Hospital Setting

Several factors including various practices used within the healthcare facility for cleaning or disinfection, operation or maintenance of fresh air purification system and the installation and maintenance of filtration system installed and maintained can affect the IAQ in hospital settings.

Rampant use of chemicals and disinfectants

Rampant use of chemicals and disinfectants by housekeeping employees for keeping the building clean is a prominent source of IAQ contamination. The chemicals used for cleaning can introduce the objectionable smell in to the indoor environment and the wet surface left after cleaning can lead to the menace of mold growth.

Ventilation system in the hospitals

The ductwork within the hospital building used to distribute air throughout the facility can become dirty over a time period and trap various contaminants such as dust, dirt, and even biological organisms. Moisture from HVAC humidification can condense within the duct system and can also seep in from breaches in the building envelope, concealed leaks, or even overspray from the cleaning process. This moisture can initiate mold growth over time, which is often left undetected until the problem becomes substantial.

Concentration of outdoor air

Outdoor air quality can also be a potential detriment to IAQ. Air quality within the healthcare facility depends upon the conditions of outdoor air and from where it is drawn. At times, harmful contaminants may be drawn along with outdoor air if outdoor pollutant source is present near to the fresh air intake point e.g. Traffic and emergency-generator exhaust are the two very common contaminants can be drawn in with the outdoor air intake.

Inappropriate filtration system

Insufficient (where not enough filtering is provided) or deficient (where filters have not been properly replaced when necessary) filtration within the air-handling systems also offer the opportunity for various contaminants to be distributed via the airstreams throughout the building.

Methods to ensure acceptable IAQ in hospitals

Clean fresh air is likely the first thing that comes to mind when one considers the concept of good IAQ. In order to achieve acceptable IAQ, the system that delivers fresh air to spaces within a building, the entire path travelled by the fresh air, contaminant sources identification must be analysed and mitigated carefully before designing the mechanical system. After the installation of right fresh air supply system (FASS), proper maintenance of the system is required for maintaining healthy indoor air quality. Acceptable IAQ within the hospital premises can be achieved through following steps:


Safe, comfortable and healthy environment to the patient, visitors and healthcare staff can be provided through ventilation. ASHRAE handbook provides specific ventilation requirements for different areas of the hospital. This handbook provides specific requirements for ventilation and filtration to dilute and remove contamination such as airborne microorganisms, viruses, hazardous chemicals and radioactive substances. ASHRAE has also specified the different temperature and pressure requirement for different areas and these requirement changes as per season and occupancy level.

Indoor air pollutants can be diluted through effective mechanical ventilation by introducing filtered outdoor air into the hospitals and exhausting the contaminated indoor air.

Fresh air intake path in to the building starts from the point from where it enters the building. Fresh air intake into the building should be located in such a way that it is not taking any contamination from any major outdoor source. Vehicular traffic and emissions from different building or factories and machinery exhausts could be the possible reason of high pollutant level in the fresh air coming into the building. Ventilation rate depends upon the outdoor air quality, season and the total area that needs to be served. Once the fresh air is drawn into the system it needs to be filtered at different steps.


Contaminant including airborne particles and microbiological pathogens can be trapped effectively in filters and removed from the circulating air. For a healthcare facility, proper filtration system must consist of prefilters, Electronic filters, HEPA filters, Carbon filters and UV light.

Prefilters with 25-30 per cent dust spot efficiency can be used in the air handing unit before the final filters. Use of prefilters helps in maintaining the prolonged life of other filters. In addition, these are easy to maintain comparative to other filters and are also cost effective. Final filters High efficiency particle arrestance (HEPA) and ultra- low particulate arrestance (ULPA) should have at least 90 per cent efficiency to collect particles, fungal spores and colony forming bacteria.

Different requirements for the filtration system can be adopted from different IAQ standards. Different types of filters are rated in terms of efficiency with a minimum efficiency reporting value (MERV).

Ventilation system to reduce hospital infections.
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As per the ASHRAE standard 52.2: Methods of testing general ventilation air-cleaning devices for removal efficiency by particle size MERV rating for the filters range from lowest efficiency at 1 to highest efficiency at 16. Filters with MERV rating 1 can capture particle larger than 10 micron (dust and pollens) and filters with MERV rating of 16 can retain particles of 0.3 micron (smoke and bacteria). HEPA filters are 99.97 per cent efficient at removing particles 0.3 microns in size and ULPA filters are 99.999 per cent efficient at removing particles of 0.02 microns in size.

Gaseous pollutants can be filtered with chemical filters. Carbon filter is the most common type of gasphase filter used in hospitals. Charged particles can be trapped with electronic air filters. Electronic filters work best for the particles less than 10 micron in size. To achieve disinfection in hospitals, Ultraviolet germicidal irradiation (UVGI) disinfection can be the best mean through which it can be achieved. UV radiation is the most commonly used in the air handling units (AHUs), cooling coils, duct works and insulation to reduce fungal growth. UV radiation of wavelength 220–300 nm can penetrate cell walls and inactivate tiny airborne droplet nuclei by disrupting their reproductive mechanisms.

Air Change Rate (ACH)

ASHRAE standard has recommended the total air change rate for hospitals in term of air changes per hour (ACH). The outdoor air change rates are based on the outdoor air quality and total space need to be served with fresh air. Outdoor air must be treated first to reduce the contamination before it is drawn into the hospital facility. 100 per cent ventilation is required in the critical areas of the hospitals like operation theatres and delivery rooms. In some areas, air change rate is highly dependent on the number of occupants serving for the pollution concentration in the area.

Differential pressure control

It is of utmost importance to maintain a differential pressure between two adjacent areas, such as isolation room and corridor to prevent hospital acquired infection. In order to ensure clean to less clean air flow in the hospital, air pressure distribution among hospital facility should be controlled efficiently. Interference due to door opening, elevator movements, leakages and other activities should be taken under consideration. These interferences can be taken care of, if differential pressure is maintained at least 2.5 Pa (0.01 in. of H2O). Constant attention to air balancing is basic requirement to maintaining a differential pressure. Pre-filters and HEPA filter load can cause the pressure drop and reduce the fresh air supply and thus a positively pressurised space can become negatively pressurised. Thus, the regular maintenance and attention of filtration system is required. Leakages within the building, ducting system needs to be identified and should be taken care. Tight fitting door with a door grille, proper insulation of the ducting system should be used to facilitate the differential pressure control.

Directional Air movement

Within in an enclosed environment air flow should be as per clean to less clean zone principle. Air must flow from clean to progressively greater contaminated area. In hospitals especially in operation theatres unidirectional airflow should be maintained to avoid undesired air turbulence. Air turbulence may result in the mixing of airborne pollutant /pathogens that in turn increase the risk of hospital acquired infection. Horizontal (from wall to wall) and vertical (from ceiling to floor) unidirectional flow method must be used in the hospitals. Contaminants spread by the surgical team can be removed effectively by Vertical air flow. In vertical air flow clean air comes from the ceiling vertically towards surgical site and takes all the contaminant towards the exhaust to the side of floor level. To check the actual air flow direction a simple smoke test can be performed to see the flow of air. Accordingly the necessary measures can be taken to maintain the unidirectional airflow.

Maintenance of the fresh air ventilation system

Maintaining the mechanical ventilation systems is very essential for the effective operation and outcomes of the fresh air ventilation system. Otherwise the risk of unwanted IAQ conditions may arise within the hospital premises even if the correct ventilation system is installed.The need for the maintenance can be signaled by performing IAQ parameters testing. IAQ parameters testing should be performed time to time to ensure healthy environment within the hospitals. It will also help to identifying the type of contamination of a given ventilation installation.

It is recommended to check and clean the ventilation and ducting system once a year or every two years, but everything depends on the quality of the air in the area, the type of ventilation or the building material.

Different parts of central air-conditioned system demand different maintenance procedures at different time intervals. Prefilters in the air handling units (AHUs) need to maintain weekly and can be washed. Whereas the electrostatic precipitators (ESPs) should be maintained twice a week depending on the outdoor pollution level in the area. ESP should be washed with water at very high pressure to remove particles deposited within the plates of ESP. Cleaning method is different for the different type of filters. HEPA filters should be cleaned weekly to maintain the acceptable IAQ and to prevent filters from getting clogged or choked. These filters can be vacuumed to remove the particles deposited between the different plates of filter. Activated carbon filters can also be vacuumed but mainly it needs replacement after a particular time period. UV lamps within the air handling unit, cooling tower and ducting should be maintained on a weekly basis to ensure the effective working of the ventilation and filtration in the HVAC system.

One can choose any one of the following method of cleaning the ventilation system as per the requirement:

Brushing: In ventilation ducts, brushing is the most common and effective solution of maintaining it. Cleaning robots or devices with flexible rollers and brushes can be used to perform the cleaning of ducting system.

Vacuuming: It is an extremely effective method of maintaining the filters within the air handing units and easily accessible ducts or in large ducts, if a specialist can enter inside.

Compressed air: This method should be used instead of a brushing and can serve as an efficient method of dealing the area with limited access.

Steam and high-water pressure: Water is mixed with detergent and high-pressure water stream is used to remove the impurities from the areas of limited access and greasy contaminations.

Mechanical ventilation systems in hospital buildings should be designed and operated not only to heat and cool the air, but also to draw in and circulate outdoor air. This system itself may contribute to the indoor air problem if it is poorly designed, installed and maintained.

Health and wellbeing are the very important benefits of the carefully installed and maintained ventilation system in any building including the hospital facilities. Regular cleaning and time to time replacement of the filters in the ventilation system reduce the risk of poor indoor air quality in the hospitals. Intake of right amount of filtered fresh air per person or as per space requirement, maintenance of the right pressure gradient within the different spaces of hospital and regular maintenance of all the Heating, Ventilation and Air conditioning systems can surely help in improving the indoor air quality of the hospitals.