P roper air quality for breathing plays very important role in human living. Breathing is the most necessary part of human being life, generally, an average person breathes aproximately 15 -20 kg of air per day. This is much greater than the average food and water consumption per day. Hence, it is very important to control the quality of air for better living mostly in hospitals and other healthcare facilities (Table 1). In hospitals where the patient enters with critical cases of disease or various infections, it is very important to have a good quality of air circulating inside the premises for not only providing better health to patients but also to keep the others feeling safe and healthy surrounding to the patients like doctors, nurses, hospital staffs, relatives of patients etc. Air quality inside the premises shall be affected by many internal as well as external parameters. The major role played in contamination of air is various bacteria, people inside the room, bio-effluents, furniture, equipment etc. Hence, it becomes very necessary to control these ontaminations with the use of modern value engineering. Healthcare facilities and hospitals have to pay particular care to indoor air concerns (Figure 1).
Now-a-days, there are so many governing agencies that provide detail guidelines to be taken care to enhance the quality of air before certifying any hospital premise. In India, we follow ISHRAE or ASHRAE Standards 170 for designing of various types of air treatment equipment for hospital and healthcare facilities. Hospitals require efficient heating, ventilation and air conditioning (HVAC) systems to maintain good indoor air quality (IAQ), aseptic conditions, and to secure healthy, safe and suitable indoor thermal conditions (i.e. temperature, humidity, air quality and airflow). There are various norms specified for various areas in hospitals. For example, for operating theatres (OTs) where patients are treated for various diseases, have very strict IAQ requirements, while, by contrast, hospital offices have practically the same requirements as any regular offices. Factors such as low ventilation rate, inadequacy of building HVAC systems, use of certain building materials and overcrowding, may result in indoor air pollution. In many countries, they follow various norms or guidelines for designing of hospital air treatment equipment.
In India we follow ASHRAE standards (62.1) for designing the HVAC systems for hospitals or healthcare facilities which provides various guidelines for designing and selection of various equipment like AHU, ducts, filters, cooling coils, ventilation systems etc. for different area requirement.
Effects of Poor Indoor Air Quality
With outdoor air pollution becoming worse every year, maintaining good indoor air quality at hospitals has become even more challenging but no less important. IAQ encompasses a wide variety of factors such as humidity, temperature, quantity, the presence of chemicals and other contaminants, and the quality of outdoor air brought inside. These are typical metrics used to define IAQ. To add to this, hospitals are normally served by a centralised HVAC system with ducts distributing cooled air to various compartments, wards, rooms etc. The presence of microorganisms in the air, especially, those from sick patients circulate freely from one area to another and result in cross contamination which poses a grave risk to patients with compromised immunity, along with doctors, nurses, visitors, and staff.
Hospitals with poor or ineffective HVAC systems are at a higher risk of incubating illnesses caused by airborne contaminants, and these illnesses will have a debilitating effect on the productivity of hospital staff as they will either have to work at reduced capacity or miss work entirely due to respiratory illnesses. Patients who suffer from diseases may be a source of contaminants (Figure 2) that can settle on surfaces or clothing and become airborne, thus, affecting other people in the facility. Poor air quality may also affect patients at the hospital. Hospital cleaning staffs often use high-grade chemicals to clean rooms and surfaces. These chemicals may create toxic gases that become airborne and can affect the well-being of patients, especially, those with compromised immune systems.
Sick Building Syndrome (SBS)
The issue of improving air quality in buildings has previously been mainly related to SBS. It is a situation in which occupants of a building experience linked to time spent in the building with no specific illness. Symptoms of SBS are acute discomfort, headaches, dizziness, eye, nose, throat irritation, dry cough, itchy skin, nausea etc. Recently, many researchers and investigators have worked on SBS issue and its effect on office workers and noticed that SBS is not linked to the type of ventilation or air conditioning system used but it is more likely to be a function of how well system are installed, managed and operated. Therefore, operation & maintenance of HVAC systems in hospitals are more critical than other buildings (Figure 3).
Different Strategies to Control IAQ in Hospitals
IAQ of a healthcare facility by definition involves a variety of factors such as thermal (temperature and relative humidity) conditions, presence of chemical components and contaminants as well the outdoor air quality. Maintaining a healthy IAQ and demands immediate attention of hospital authorities towards taking the necessary measures to maintain a sound and healthy atmosphere for the patients, healthcare workers and others.
Active Ionisation Technology to Improve IAQ
Active Ionisation technology has an elevated anti-bacterial power and is proven to be active on pollen, fine dust, toner, mould, smog, viruses, bacteria and tobacco smoke. These contaminants, according to their size, can enter the body and damage certain organs. Among the most dangerous airborne substances Legionella, a very topical problem that causes millions of deaths every year. With Ionisation air cleaners, this problem is eliminated as pollen, dust mites, fungus and other contaminants are captured and inactivated. This echnology is extremely efficient and is proven at removing 98-99 per cent of:
• Airborne bacteria, such as Micrococcus luteus;
• Yeast, such as Rhodotorula rubra;
• Bacillus Anthracis;
• Moulds and germs present in the natural spectrum of air.
Maintaining the Humidity Levels
The heating, ventilation and air conditioning systems of buildings and their components, as well as sanitary equipment, can nurture and amplify the diffusion of airborne substances. Among these, Staphylococcus Aureus and Legionella are seen as particularly dangerous. The first cases of legionellosis were, in fact, attributed to airborne substances containing bacteria from cooling towers, evaporative condensers or humidification sections of the air
handling units of AC systems. Infections are also caused by contamination of water supply networks, sanitary appliances, oxygen therapy equipment, fountains and ultrasonic humidifiers.
Ultraviolet Germicidal Irradiation (UVGI)
Ultraviolet Germicidal Irradiation (UVGI) is a proven method for removing volatile organic compounds (VOCs), and for killing or deactivating bacteria, viruses, mold spores and other pathogenic microorganisms that may be present in room air. Ultraviolet light is electromagnetic radiation with a wavelength of 254 nanometer which is capable of breaking molecular bonds within micro organismal DNA. UV technology is superior to traditional disinfection in many ways. However, proper validation is a prerequisite for the success of UV technology in air disinfection. The use of UVGI air disinfection systems (Figure 4) in air handling units (AHUs) is highly effective in maintaining a clean evaporator and coils by preventing the growth of bacteria on the coil surfaces. This enhances the energy efficiency of the AHU, resulting in reduced energy costs and lower maintenance costs. The use of UVGI air disinfection systems reduces unpleasant odours which may result from outside air or re-circulated air within the building.
High Efficiency Particulate Arrestance (HEPA) Air Filters & Ultra Low Particulate Arrestance (ULPA) Air Filters
Filter air to reduce airborne particle counts to levels appropriate for each facility and function. Minimum filter efficiency should be 90 per cent of particles 0.5 microns and larger. In facilities, where patients are at the greatest risk of airborne infection, such as operating rooms and rooms for bone marrow transplant patients, deliver supply air through high efficiency particulate air (HEPA) filters. Particulate filters are typically provided in pleated media, bag, and cartridge types. In critical spaces, filters are not just used in the air handling equipment, but also at supply diffusers or grilles, which are the point of air delivery to the space, where they act as the last line of defense to keep contaminants from entering the space (Figure 5).
Gas-phase filters are chemical filters. The most common types of gas-phase filters for general filtration at hospitals and other healthcare facilities use either activated carbon or potassium permanganate (often referred to as purple ellets). Consider the use of gas-phase filters when it is impossible or impractical to locate intakes sufficiently away from irritating, corrosive, or odorous airborne contaminants.
Electronic air filters typically either incorporate charged plates or wires. They electrostatically charge the particles as they pass to aid in arresting the conveyance of the particles. This type of filter generally works best on particles that are less than 10 microns in size. Electronic filters that incorporate charged plates don’t require regular media replacement, but do require regular cleaning.
Tracking Airborne Gases
Carbon dioxide (CO2) is a natural byproduct of human respiration. So, it can be used as an indicator of IAQ. If CO2 levels are excessive, you can assume that other gases – such as volatile organic compounds (VOCs) emitted by building materials, paints, and carpets – are also building up. CO2 levels beyond 1,000 ppm may show that not enough fresh outside air is being mixed into the indoor air supply to dilute gases. One can measure CO2 levels with a handheld meter. Carbon monoxide is a poison. One can use both fixed and handheld CO testers to detect the presence of this dangerous gas.
Distributing Quality Air
Once the air has been brought into the building from a clean location, been filtered appropriately, heated or cooled to the proper temperature, and humidified or dehumidified as needed, it must then be distributed to the various spaces throughout the building. The applicable codes and standards will dictate the minimum amount of fresh air ventilation and total air exchanges needed for the various healthcare spaces. For example, ASHRAE Standard 170-2013 and the 2014 FGI Guidelines indicate that patient rooms must have a minimum of two air changes per hour of fresh air ventilation and 4 ACH of total air movement. Class B operating rooms must have 4 or 6 ACH depending on room type, of fresh air ventilation, and 20 ACH of total air movement. While the quantity of air distributed to the space is important, from an air-quality standpoint, space pressurisation is perhaps even more important. Designers must be certain that the air quantities are balanced so that air travels from the cleanest spaces (such as operating rooms) to the dirtiest spaces (such as soiled utility or decontamination rooms). IAQ is an important component to the design of any building, and it’s vital when designing a hospital or healthcare facility. Proper consideration must be taken to ensure that clean, fresh air is brought into the building, that the air is maintained within specific parameters for temperature and humidity, and that the air is not allowed to contaminate other spaces as it is routed back through the system (Figure 6).
A key step is to establish pressure relationships that move air from clean environments (higher pressure) to dirty or contaminated areas (lower pressure). One can create pressure differentials by using exhaust fans (as in a restroom or construction area) to reduce pressure, by increasing air supply to boost pressure, and by combining these measures. By stopping leaks in ducts, windows, ceilings, and doors, one can reduce uncontrolled air movement that can disrupt air flow patterns.
Architects and engineers must design healthcare HVAC systems to control airborne infectious agents and pollutants, manage air pressure and direction of flow, and deliver other air conditions required for the health and comfort of patients and staff. Numbers of challenges have been found in maintaining the good IAQ for hospitals and healthcare facilities while supplying air hrough air handling unit (AHU) to various critical areas. Different strategies may have been used for cleaning the air before supplying to hospital premises. It could be concluded some basic criteria are as followed:
• No cross movement of air is allowed in and between the various departments of the hospitals to avoid contamination and viral infections etc.
• Direct discharge of inside air to the atmosphere shall be restricted. Air should be treated to remove or kill various bacteria or infectious viruses before discharging outside of the premises.
• To control air quality, one require various filtrations starting from 20 microns to 0.3 microns or more depending on the need of area.
• The specific requirements of ventilation system to ensure sufficient flow of air volume for supply inside the premise as well as for exhaust outside the premise.
• Ventilation effectiveness should be taken care to maintain appropriate indoor air quality.
• To enhance indoor air quality (IAQ) requires necessary filtration which shall be capable to remove or dilute contamination in the form of odour, airborne microorganisms, viruses, hazardous chemicals and radioactive substances etc.
• The various temperature and humidity requirements for various areas and the accurate control of environment condition.
• The prime motto of design should be to minimise the risk of hazardous chemicals, bacteria and viruses in air and provide a comfortable and healthy environment for patients and working staff.
To achieve these parameters require very high quality of outside air along with significant treatment of this outsides air before entering to the premise, which requires cooling, reheating, humidifying and filtration of air.
Dr. D.B. Jani
Government Engineering College, Dahod,
Gujarat Technological University – GTU,