Thursday, 9 January 2014


Ventilation (the V in HVAC) is the process of "changing" or replacing air in any space to provide high indoor air quality (i.e. to control temperature, replenish oxygen, or remove moisture, odors, smoke, heat, dust, airborne bacteria, and carbon dioxide). While heating and air-conditioning are relatively straightforward operations, the more complex processes involved in ventilation are the most important in determining the quality of our indoor air.

It is one of the most significant engineering controls available to the industrial hygienist for improving or maintaining the quality of the air in the occupational work environment. It is a means of controlling the environment with air flow. Ventilation also assists in removing unpleasant smells and excessive moisture, introduce outside air, to keep interior building air circulating and to prevent stagnation of the interior air. Ventilation is addressed in specific standards for houses, offices, general industry, shipyard employment, long shoring, and the construction industry. Currently a number of well-identified illnesses, such as Legionnaire’s disease, asthma, tuberculosis, the common cold, influenza, meningitis, hypersensitivity pneumonitis and humidifier fever, have been directly traced to specific building ventilation problems. These are called building-related illnesses and are increasingly predominant in common buildings and workplaces today. Most of these diseases are treatable but some pose grave health risks and may require prolonged recovery times, most often long after the person has left the building.

There are many types of ventilation options –

Single - Sided Ventilation: limited to zones close to the openings

Cross - Ventilation: two or more openings on opposite walls - covers a larger zone than the single-sided openings

Stack Ventilation: Buoyancy - driven gives larger flows

Windcacthers: Wind and buoyancy driven-effective in warm and temperate climates

Solar - induced Ventilation: using the sun to heat building elements to increase buoyancy – more effective in warm climates

Mechanical or forced ventilation: through an air handling unit or direct injection to a space by a fan. A local exhaust fan can enhance infiltration or natural ventilation, thus increasing the ventilation air flow rate.

Natural ventilation: the airflow is due to wind and buoyancy through cracks in the building envelope or purposely installed openings.

Mixed Mode Ventilation or Hybrid ventilation: uses both mechanical and natural ventilation processes. The mechanical and natural components may be used in conjunction with each other or separately at different times of day.

Mechanical exhausts control odors and humidity in kitchens and bathrooms. Ceiling, table, floor fans circulate air within a room for the purpose of reducing the perceived temperature because of evaporation of perspiration on the skin of the occupants. When creating an energy-efficient, airtight home/ workplace through air sealing, it's very important to consider ventilation. Unless properly ventilated, an airtight home can seal in indoor air pollutants. Opening doors, windows, and using ceiling fans are all ways to maximize natural ventilation and reduce the risk of airborne contagion. Natural ventilation requires little maintenance and is inexpensive. Ventilation also helps control moisture, which is another important consideration for a healthy, energy-efficient home.

Good ventilation is matter of great criticality, ISO 16813:2006 is one of the ISO building environment standards, applicable to new constructions and the retrofit of existing buildings.  “It considers the need to provide a healthy indoor environment for the occupants as well as the need to protect the environment for future generations and promote collaboration among the various parties involved in building environmental design for sustainability.”

If you or others at your home/office are experiencing health or comfort problems that you suspect may be caused by indoor air pollution, you can talk to other family members or colleagues to see if similar problems are being experienced by others and contact a HVAC specialist immediately.

No comments:

Post a Comment