The moment one enters a large office space or a corporate hospital, one breathes a sigh of a relief. The floor is spotless, the furnishings are clean, and the air is cool – this seemingly immaculate environment is something we take for granted, without realising that what we are inhaling as breaths of fresh air may be loaded with lethal germs that can destroy our health.
What maintains comfort inside a building? The centralised HVAC system, which is like a network of blood vessels that give off branches to every room, maintaining a certain temperature and relative humidity. These mostly unseen ducts create an artificial environment inside a facility, which we feel is superior to the hot, grimy outdoors. But if the duct system and the cooling machinery isn’t regularly cleaned and maintained, the system degenerates into something that transfers germs from one interconnected room to another.
For example, the same HVAC system supplies air to both an operation theatre in which an infected wound is being operated upon, and an ICU which must remain sterile. The OT and the ICU are connected to each other by ducts; imagine the consequences of air from the former being pumped into the latter. Centralised cooling is a great concept on paper, but also has the potential of becoming a centralised dispenser of germs; think of an office environment in which employees spend 8-10 hours a day, six days a week, in which an ill-maintained HVAC system itself causes illness.
In recent years, India is paying a lot of attention to outdoor air quality. Most of us have forgotten about the other half of air quality: indoor air quality. The US Environmental Protection Agency (EPA) estimates that we spend 80-90% of our time indoors; hence, indoor air quality affects our quality of life to a far greater degree. It was ranked by the EPA as among the top five environmental health risks to public health.
What is indoor air quality (IQA)? It is loosely defined as the quality of air inside the building, as represented by concentrations of pollutants and thermal (temperature and relative humidity) conditions that affect the health, comfort, and performance of the occupants. Facilities such as commercial offices and manufacturing facilities should be concerned about their IQA if they are concerned about the comfort and efficiency of their employees, while hospitals – where people come to recover their health – need to pay attention to the air inside hospitals which can adversely impact health.
Sick building syndrome (SBS) is a condition in which building occupants experience acute health and comfort effects which are linked to the time spent in the building by them, but with no specific illness or cause identified. It is not a clinically diagnosable disease. Inadequate ventilation is the main cause. Its symptoms are diverse, and include eye or throat irritation, headache, dizziness, fatigue, difficulty in concentration, dry or itchy skin, and nausea.
Carbon dioxide is generated inside a building primarily by human metabolism. Build-up of this gas indoors indicates inefficient functioning of the ventilation system, and is a good indicator of ventilation rates. According to the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE), an indoor carbon dioxide level of more than 1000 parts per million can cause SBS symptoms, and requires adjustment of the ventilation system.
Sources of indoor air pollution
• Volatile organic compounds from cleaning products, insecticides, pesticides, aerosols, paints, solvents.
• Suspended particulate matter from carpets, paints and polishers.
• Gases like carbon monoxide, nitrogen oxides and sulphur dioxide. Effects of these pollutants on the occupants of a building:
• Respirable Suspended Particulate Matter: Diseases of the upper and lower respiratory tract, asthma, chronic obstructive lung disease, lung cancer.
• Volatile organic compounds: Liver and kidney disorders, irritation to the eyes, nose and throat, skin rashes and respiratory problems.
• Pesticides: Skin diseases
• Nitrogen oxides: irritation to the skin, eyes and throat, cough.
• Carbon monoxide: Headache, shortness of breath.
• Sulphur dioxide: Lung disorders and shortness of breath
Temperature
It also found that at elevated air speeds above 0.2 m/s (39 feet/min), the upper limit of the temperature range can be relaxed, as employees still find the air quality bearable.
Relative humidity
Too high relative humidity can contribute to the growth and spread of biological contaminants, and stimulate increased perspiration, while too low a value causes increased discomfort and drying of skin and mucous membranes. As per ASHRAE standards, indoor humidity levels to be maintained between 30-65% for optimum comfort.
Micro-organisms
Indian scenario
The most important factor influencing indoor pollution is the level of outdoor air pollution. Construction material used in Indian buildings are usually not airtight; this creates a negative pressure inside the building. In a process known as infiltration, outdoor air flows into the building through openings, joints, and cracks in walls, floors, and ceilings, and around windows and doors, bringing in moisture and pollutants.
According to India’s Central Building Research Institute, Indians are more adaptive to high temperatures during summer, have a higher tolerance for humidity, and comfortable if the air flow velocity inside a building is on the higher side. By using an adaptive temperature control method and setting the thermostat to have a floating set point rather than a fixed one, a 15% energy saving potential can be tapped.
The Indian Society of Heating, Refrigeration and Air-Conditioning Engineers (ISHRAE) recommends that rather than a rigid temperature range, operative and effective temperatures be used for controlling indoor quality, taking into account the combined effect of air temperature, humidity, and the activity and clothing of the occupants. ISHRAE recommends that both high and low humidity need to be avoided.
Monitoring
The monitoring protocol should also include the schedule of measurements, the specifications of the measurement equipment’, how to select the representative spaces in the building for monitoring, and how to select the sampling sites in each space. ASHRAE recommends that monitoring be done at least three location inside a building. At least 5% of rooms in offices, 10% of classrooms in educational institutions, and 15% of rooms in a healthcare facility should be selected for monitoring IQA.
IQA parameters need to be measured over a period of time. Short time sampling/monitoring (< 15 min) is chosen for investigating acute effects, while the investigation of chronic effects is done by carrying out sampling/monitoring for longer duration of several hours or even days.
For the Indian scenario, the monitoring durations proposed are:
• Schools / colleges /educational institution: two working hours)
• Offices: two working hours
• Health care units: morning and evening, one hour in each case
• Restaurants: two hours in the evening
• Museums/Historical Buildings: two hours during visiting hours)
• Industrial establishments: short time or long time monitoring during working hours
The sampling duration must represent both ‘peak’ exposure and ‘average’ exposure indoors. For chemical characterization of pollutants/microorganisms, long duration monitoring is required.
Management of Indoor Air Quality:
• Routinely cleaning office spaces and common areas by a vacuum cleaner with High-Efficiency Particulate Air (HEPA) filter
• Maintaining and regularly cleaning the building heating, ventilation, and air conditioning (HVAC) system
• Properly storing cleaning materials and chemicals that are used in the workplace
• Avoiding the use of harmful chemicals that emit volatile organic compounds
• Maintaining air purifiers and ensuring regular cleaning and replacement of filters
• Air curtains installed at main entry/exit doors of the building to prevent entry of outside air when outside doors are open
• Silicon sealing of all window gaps and installation of door dust brush underneath the doors, to prevent dust from coming into the building
• Installation of air pollution monitoring devices for improved, regular monitoring of the indoor air quality
• Wet mopping and dusting is preferable to sweeping or vacuuming, as sweeping and vacuuming can stir up additional dust and particles. However, vacuums with a High-Efficiency Particulate Air (HEPA) filter can be used.
Compiled by Mrigank Warrier