AC and Ventilation for India

Many homes and almost all offices today are using air conditioning systems. Air conditioning for many may be a luxury, but it is a necessity for some people. These systems are used for heating, ventilation, and air conditioning in other countries and are generally referred as ‘HVAC’ systems. However, both heating and cooling in one unit are not available in India. And due to lack of awareness on key functions of air conditioning systems most of the people in India ignore ventilation.

This article makes you aware of the key features of air conditioning systems and helps you to take better care for them and use them well.

Key functions of an Air Conditioning system
Many people have a common misconception that air conditioners are needed only to cool the indoor air to provide ambient indoor climate. In fact, it has to perform many other key functions in order to provide a good indoor air quality.

  • It needs to remove excessive humidity from indoor air during certain seasons
  • Should provide adequate and constant ventilation-remove carbon dioxide and circulate fresh air with oxygen
  • It should remove micro-organisms from the air
  • Needs to remove dust, soot, pollen and other foreign bodies from the indoor air
  • It should efficiently cool the room air when needed
  • It should provide hot air in winters
  • It needs to remove volatile organic compounds (VOCs) from the indoor environment
  • It needs to remove dangerous gasses such as carbon monoxide

Everybody knows at what temperature they feel comfortable and adjust the temperature with the help of remote control. However, people don’t know whether their air conditioner performs all the above-mentioned functions or how important these are.

Whether your air conditioner provides it or not, ventilation is very necessary. Air contaminants generated indoors are dangerous and can lead to significant health problems. Adequate ventilation makes sure that the occupants indoors are inhaling fresh air. The American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) recommends that there should be enough ventilation to exchange the indoor air at least once every four hours depending on the design of the house.

Inadequate ventilation depletes the oxygen content, increases the carbon dioxide levels, circulates VOCs, dust particles including pollen and other microorganisms and dangerous gasses such as carbon monoxide.

Many of the air conditioning systems re-circulate a significant portion of the indoor air to reduce energy costs. Thus use of air conditioning systems in closed working environment with out good ventilation may reduce the availability of oxygen to the brain. Low content of oxygen in the air causes headaches and other health related problems. There should be a constant inflow of up to 10% of filtered, fresh air into an air-conditioning system to maintain the required oxygen levels in the indoor environment.

Carbon dioxide
Carbon dioxide is a colourless, odourless gas, which is constantly released by humans in the process of breathing. An effective air conditioner should dilute these CO2 levels regularly by introducing some outside air. But most of them are in effective in reducing the CO2 levels. Due increasing levels of carbon dioxide occupants feel drowsy, get headaches and their activity levels get reduced. The level of the CO2 can be used as an indicator of ventilation. ASHRAE recommends that indoor CO2 concentrations should be maintained below 1,000 ppm in schools and 800 ppm in offices and 600 ppm in homes compared to outdoor levels.

Air particulates
Dust, fumes, smoke, and organisms such as viruses, pollen grains, bacteria, and fungal spores may come from both indoor and outdoor sources. Almost every air conditioning system has a filter in the evaporator coil. This filter removes particles from the indoor air to remove particles from the air as well as to keep the air conditioning system clean by blocking the dust particles entering into the system. The air conditioning units filter the pollen, mold spores, and dust, which can cause allergies and asthma.

Humidity & Temperature
Generally air conditioning systems reduce the humidity of the air as they cool. Temperature and relative humidity are two factors that affect the indoor thermal comfort. Humidity levels below 25% can result in drying of the mucous membranes and skin, leading to chapping and irritation. Low relative humidity also hinders the operation of computers and paper-processing instruments. High humidity levels results in the development of mould and fungi on the walls. So, ASHRAE recommends humidity range to be between 25 and 60%.

Carbon Monoxide
Carbon monoxide is extremely toxic, colourless, and odourless gas generally evolved due to incomplete combustion of materials. It reduces the supply of oxygen to the body. At high levels, it causes headaches, decreased alertness, flu-like symptoms, nausea, fatigue, rapid breathing, chest pain, impaired judgment and confusion. ASHRAE recommends that the average exposure of 8-hours limit for carbon monoxide should not exceed 9 ppm. The air conditioning system should provide adequate ventilation to remove the CO levels from indoors.

Volatile Organic Compounds
Volatile Organic Compounds are chemicals, which contain carbon and hydrogen. There are several thousands of VOC types. The sources for the most common ones are paint, paint remover, gasoline, and carpet. Exposure to VOCs may trigger fatigue, headaches, drowsiness, dizziness, weakness, joint pains, peripheral numbness or tingling, euphoria, tightness in the chest, unsteadiness, blurred vision, and irritation in the eyes and on the skin. Air conditioning systems with good ventilation reduce VOC emissions in the indoor climate.

All the above mentioned functions need to be performed the air conditioners in order to have a good indoor air quality.

Note: We could not find any standards for India, so we have used ASHRAE (American Society of Heating, Refrigerating, and Air Conditioning Engineers), since they seemed reasonable and applicable in Indian context also.

Reproduced with permission from