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Frequently Asked Questions (FAQ)

FAQ - 1

1. Why is indoor air quality important?

On average, we spend more than 70-90% of our time indoors, be it office, home or other indoor environment. Polluted indoor environment can cause headaches, itchy eyes, respiratory difficulties, nausea, skin irritation and fatigue. People with respiratory issues are more susceptible to the effects of polluted indoor air. Improved indoor air quality can result in staying healthy with more productivity.

2. What are the causes of poor indoor air quality?

Our indoor environment is undergoing a continuous change due to various factors. These factors include sources of pollutants, maintenance and operation of building ventilation systems, temperature and humidity.

3. How do I know if there is indoor air quality problem?

It can sometimes be difficult to tell if you have an indoor air quality problem. You should pay attention to any allergy or breathing-related symptoms that you or your family or your colleague may have been experiencing recently. You should also keep an eye for growth of molds, which is a leading contributor to indoor air pollution. Make sure that the vents in your indoor facility i.e. home or office are working effectively. You may also want to have someone come out and take a look to see if there are any leaks or cracks in your office ventilation system or your duct work.

4. What is Sick Building Syndrome (SBS)?

Sick building syndrome (SBS) is a medical condition where people in a building suffer from symptoms of illness or feel unwell for no apparent reason.  This can be identified with an increased incidence of complaints of symptoms such as headache, eye, nose, and throat irritation, fatigue, and dizziness and nausea. The causes can be due to flaws in the heating, ventilation, air conditioning (HVAC) systems, contaminants produced by  some types of building materials, volatile organic compounds (VOC), molds  improper exhaust ventilation of ozone  light industrial chemicals used within, or lack of adequate fresh-air intake/air filtration.

5. Which pollutants cause poor indoor air quality?

Typical pollutants include:

  • Combustion byproducts such as carbon monoxide, particulate matter, and environmental tobacco smoke
  • Substances of natural origin such as radon, pet dander, and mold
  • Biological agents such as molds
  • Pesticides, lead, and asbestos
  • Ozone (from some air cleaners)
  • Various volatile organic compounds from a variety of products and materials

Most pollutants affecting indoor air quality come from sources inside buildings, although some originate outdoors.

6. What are the sources of indoor pollutants?

Common indoor sources of pollutants are: 
Combustion sources in indoor settings, including tobacco, wood and coal heating and cooking appliances, and fireplaces, can release harmful combustion byproducts such as carbon monoxide and particulate matter directly into the indoor environment.

Cleaning supplies, paints, insecticides, and other commonly used products introduce many different chemicals, including volatile organic compounds, directly into the indoor air.

Building materials are also potential sources, whether through degrading materials (e.g., asbestos fibers released from building insulation) or from new materials (e.g., chemical off-gassing from pressed wood products). Other substances in indoor air are of natural origin, such as radon, mold, and pet dander. The pollutants can be distributed broadly into following major categories:

Biological Contaminants: Bacteria, viruses and fungi that result from poor maintenance, water spills, poor humidity control or may be brought into building by occupants or air ventilation.

Chemical Pollutants: Sources of Chemical pollutants include tobacco, smoke, ozone from photocopiers.
Particulate Matter: The sum of all solid and liquid particles suspended in air many of which are hazardous. This complex mixture includes both organic and inorganic particles, such as dust, pollen, soot, smoke, and liquid droplets.

7. What are applicable standards and guidelines for indoor air quality?

ASHRAE: https://www.ashrae.org/technical-resources/bookstore/standards-62-1-62-2
WHO: https://www.who.int/airpollution/guidelines/en/
OSHA: https://www.osha.gov/Publications/3430indoor-air-quality-sm.pdf
Local Municipalities and Authorities.

8. How can indoor air quality be improved?

Small steps can help in improving the indoor air quality. It is better to monitor indoor air quality and take appropriate steps based on the data collected.
a. Ensure sufficient air ventilation to remove the polluted air.
b. Keep changing the air filters regularly.
c. Make healthy humidity level.
d. Add some plants that improve oxygen levels.
e. Make use of air purifier.

9. How can we improve indoor air quality naturally?

A. Improve air ventilation.
B. Removal of toxins with indoor plants.
C. Use natural oils instead of synthetic fragrances.
D. Make use of natural alternatives to chemical cleaners.

10. How can indoor air quality be measured?

Latest technology indoor air quality monitors are available working on GSM technology providing online real time information on CO2, Formaldehydes, VOC’s, Particulate Matter, Temperature and humidity within a single device.

11. How is HVAC system responsible for indoor air quality?

A properly designed, installed, operated and maintained HVAC system distributes air adequately to remove odours, fumes and other indoor air contaminants. HVAC filters should be regularly cleaned or replaced. Proper functioning of air handling units ensuring proper air flow helps in removing polluted and stagnated indoor air. Regular inspection and cleaning of ducts helps in improving indoor air quality.

12. How can indoor plants help in improving indoor air quality?

There are no definitive studies to show that having indoor plants can significantly increase the air quality to improve health in a measurable way. Plants are capable of removing volatile chemical toxins from the air “under laboratory conditions.” But in the real world—in home or in office space—the notion that incorporating a few plants can purify your air doesn’t have much hard science to back it up.

13. Which parameters are commonly monitored by IAQ monitoring devices?

Carbon Dioxide (CO2), Formaldehyde (CH2O), Volatile Organic Compounds (VOC’s),
Particulate Matter (PM), PM1.0, PM2.5, PM10, Relative Humidity (RH) and Temperature.

14. Which particulate matter is most dangerous?

Particulate matter contains microscopic solids or liquid droplets that are so small that they can be inhaled and cause serious health problems. Some particles less than 10 micrometers in diameter can get deep into your lungs and some may even get into your bloodstream.

15. What are the acceptable limits of indoor air quality parameters?

The acceptable limits of indoor air quality parameters are
Carbon dioxide (CO2): 1000-1200 ppm (ASHRAE Standard 62.1-2016)
Formaldehyde (CH2O): 0.75 ppm (OSHA – Total Weighted Average for 8 hours)
Volatile Organic Compound (VOC): 300-500 ug/m3 (No regulatory standard, serves as a guideline)
Particulate Matter (PM): 150ug/m3 (EPA -24 hour average )
Temperature: 21 -23 deg. Celcius (ASHRAE Thermal Comfort Standard)
Humidity: 25-60% (ASHRAE Standard 62-2001 Ventilation for acceptable Indoor Air Quality)

16: What is ventilation and its safe limits?

Ventilation is the process by which 'clean' air (normally outdoor air) is intentionally provided to a space and stale air is removed. The typical units used are cubic feet per minute (CFM) or litres per second (L/s). The ventilation rate can also be expressed on a per person or per unit floor area basis, such as CFM/p or CFM/ft², or as 'air changes per hour' (ACH). At the activity levels found in typical office buildings, steady-state CO2 concentrations of about 700 ppm above outdoor air levels indicate an outdoor air ventilation rate of about 7.5 L/s/person (15 cfm/person).

FAQ - 2

17: What are airborne diseases?

Diseases that affect human health simply by breathing are called airborne diseases.

18: What are common airborne diseases?

Airborne disease can spread when people with certain infections cough, sneeze, or talk, spewing nasal and throat secretions into the air. Some viruses or bacteria take flight and hang in the air or land on other people or surfaces. Some of the common airborne diseases The Common Cold, Influenza, Chickenpox, Mumps, Measles, Whooping cough (pertussis), Tuberculosis (TB), Diptheria. A rapidly spreading Corona Virus, SARS-CoV-2, COVID-19.

19: What you can do to prevent spreading an airborne disease:

Although it’s impossible to completely avoid airborne pathogens, there are some things one can do to lower the probability of getting sick:
a) Avoid close contact with people who have active symptoms of disease.
b) Stay home when you’re sick. Don’t let vulnerable people come in close contact with you.
c) If you must be around others, wear a face mask to prevent spreading or breathing in germs.
d) Cover your mouth when you cough or sneeze. Use a tissue or your elbow to cut down on the possibility of transmitting germs on your hands.
e) Wash your hands thoroughly (at least 20 seconds) and often, especially after sneezing or coughing.
f) Avoid touching your face or other people with unwashed hands.

Vaccines can reduce your chances of getting some airborne diseases. Vaccines also lower the risk for others in the community.
Airborne diseases that have vaccines include: Chickenpox, Diphtheria, Influenza, Measles, Mumps, TB and whooping cough.

20: What is the difference between bacterial infection and viral infection?

Bacterial infections are caused by bacteria, and Viral infections are caused by viruses. Perhaps the most important distinction between bacteria and viruses is that antibiotic drugs usually kill bacteria, but they aren't effective against viruses.

21: How to prevent viral infection transmitted through indoor air?

Apart from hygiene and sanitary habits, ventilation and air management plays important role in preventing viral infection.
The United States Environmental Protection Agency EPA) recommend increasing ventilation to help exchange air between the inside and outside of a building.

In an unventilated area, pathogens, pollutants, and moisture can build up to unsafe levels. Cleaning the air with a filter is another part of keeping an area as free of pollutants and pathogens as possible.

22: How is Indoor Air Quality monitoring helpful for airborne infections?

The management and monitoring of indoor air quality is one important component of an effective Infection Control Management Plan.

The lung is the most common site of injury by airborne pollutants.

Poor indoor air quality increases the transmission of airborne infectious disease. A critical area in environmental monitoring, Particulate Monitoring, is key to the prevention. Long time continuous monitoring increases the health and safety of both survivors and responders. A typical IAQ monitoring device measuring multiple parameters such as microscopic particulates less than 10 microns in size, temperature, relative humidity, carbon dioxide, total volatile organic compounds, air pressure, and formaldehyde is very helpful to keep a check on Indoor air pollutants.

23:  How long can a virus survive?

There is not one answer to this question. The life of a virus (technically, viruses are not alive) depends on what type of virus it is, the conditions of the environment it is in, as well as the type of surface it is on.

Cold viruses have been shown to survive on indoor surfaces for approximately seven days. Flu viruses, however, are active for only 24 hours.

All viruses have the potential to live on hard surfaces, such as metal and plastic, longer than on fabrics and other soft surfaces. In fact, infectious flu viruses can survive on tissues for only 15 minutes. Viruses tend to also live longer in areas with lower temperatures, low humidity, and low sunlight.

24: What is the impact of disinfectants on virus?

There are three important functions that must remain intact for the virus to be infectious: it must be able to attach to the host cell, inject its material into the host cell and then be able to replicate.
Disinfectants are antimicrobial agents designed to inactivate or destroy microorganisms on inert surfaces.[Disinfectants work by destroying the cell wall of microbes or interfering with their metabolism.

25: What is a virus?

A virus is a genome and some proteins. Viruses react to pasteurization, chlorine disinfection and UV radiation.

Pasteurize, Chlorine..


Pasteurization is used to conserve a food, such as milk, for long periods of time by drastically reducing the number of micro-organisms in it. Heat inhibits the bonding with the host cell. The virus no longer recognizes the host, so it cannot attach to it.

The disinfectant properties of UV radiation have been explored for more than 100 years. Food networks or ventilation and air-conditioning systems were coupled to UV lamps in order to eliminate the propagation of pathogenic agents.

The radiation acts in two ways on a virus. First, it triggers chemical reactions that destroy the genome, so that it can no longer replicate itself in the host. In addition, it breaks the virus’ protein shell, or capsid. Because the virus’ genetic material is held under pressure in the capsid, when this shell is broken, there is no way for the virus to inject the material into the host cell.

Chlorinating drinking water and swimming pools has become commonplace. Chlorine attacks the genome, prevents it from replication and destroys its injection function.


Author: Sandy Evangelista

Source: EPFL

26: What is air change (ACH) rate?

The rate at which indoor air is replaced or filtered in a defined space is known as Air Change rate.

The table below gives recommended air change rates(air changes per hour) in some common types of rooms and buildings:

27: How to calculate Air Change Rates?

n= 60 q / V

n= desired air change rate per hour (ACPH)

q = changed air flow through the room (Cubic Feet per Minute,cfm)

V = volume of the room (Cubic Feet)

For example: 

If you have an air purifier delivering 265 cfm of air to your office measuring 20 ft. x 15 ft. with 8 ft. ceilings (2,400 cubic feet), the air change rate would be calculated as follows:

60 x 265 (cfm) / 2,400(volume of room) = 6.63 air changes per hour. 


1. http://www.engineeringtoolbox.com/air-change-rate-room-d_867.html

2. http://en.wikipedia.org/wiki/Indoor_air_quality

28: What are the typical values of Air Change Rates?