Ventilation is a process of air exchange in any place with the purpose to control temperature or replace any combination of dust, odors, moisture, smoke, airborne bacteria and refill the place with oxygen. It also involves both the movement of air in the building, which reduces pollutants supplied through breathing, activities from the house and emitted pollution from furniture and fittings in the building. This is a requirement for the maintenance of interior air quality in buildings. There are two types of building ventilation: mechanical ventilation and natural ventilation.

Natural Ventilation

Natural ventilation does not involve mechanical system; ceiling fans and floor fans with air from outside. It appears where there are trickle vents or those windows which are opening. This is usually previewed the architecture and the spaces available to ventilate are small. Where systems are more complicated, hot air inside the building can be increased and flow out through the top ventilations on the outside. This will lead to cool air from outside via the openings from the interior side to be drawn in the building naturally.

Natural ventilation is not the best thing in the humid environment especially when climate is maintaining thermal comfort instead, then air conditioning is used as a backup. The amount of air changing per hour is the rate used to emphasize the amount of ventilation moving than the air supplied, via a certain part considering the size of the area. This concept of air changing per hour is the best component of natural ventilation where air changing per hour determines the pressure in a room whether it’s negative or positive. If the amount of the exhausted air is less then it’s a positive pressure, while if the amount of supplied air is less than the air being exhausted then it’s negative.

Mechanical Ventilation

Mechanical ventilation is also known as forced ventilation which is given through an air handler and it regulates the air inside a building. Excessive odors, contaminants and moisture can be regulated through the exchange of air from outside. Mostly, it’s advisable to have toilets, kitchens and bathrooms with a mechanical ventilation to control moisture and odors in residential areas, while in non-residential areas corridors are mostly used. More energy is needed to overcome the excess humidity through the ventilation and mostly in humid weather conditions. It’s advisable to have ceilings fans and floor fans for better regulation of air around the room in order to minimize perceived temperature through rising evaporation of perspiration. Since hot air increases, ceiling fans keep the room warm during the winter through regulating the warm stratified air coming from the ceiling and moving to the floor.

Using the mechanical supply of air in the rooms, draught can be minimized through supplying as much air as possible and air coming in shall also be controlled.  Air from outside is usually transported into the building using ducts while ventilator usually controls the air being supplied. Through preheating the air coming in, draught is reduced. Due to greater pressure produced mechanically within the building, the system does not wholly depend on the weather conditions; this is usually due to the creation of under pressure in the building. Air is sucked in due to the under pressure created as a result of pressure difference over the ventilation openings. The avoidance of flu is also necessary, since in case of anybody has the flu, virus may infect the rest of people who might not be having the virus. For this reason, there is need for mechanical ventilation system. In most intensive care units, mechanical ventilation systems are used in medical transport, outside and inside the hospital, and emergency rooms. There are systems used for adult lungs ventilators and for neonates. In most of the big commercial buildings, great amount of heat is produced through the lighting, computing and other sources associated with electricity. For this reasons, mechanical ventilation systems are necessary in those skyscrapers in order to maintain the fresh air.


Characteristics of Mechanical Ventilation

  1.  The mechanical ventilator usually operates when the regulation of air is required and this can be done without the need of the occupant.
  2. This systems usually also operates when only required since there are some costs incurred for it to operate, for example, the cost of electricity, installation costs and maintenance costs. For this reasons, during the times when there is no regulation of air needed it should not be operated. Air regulation is not needed when the owner is not in the house or there is enough air distribution to meet the owner’s requirements.
  3. The mechanical system provides the amount of air regulation required by the owner. It’s able to be controlled in order to distribute the air such that it does not take in more air from outside.
  4. The air coming from outside is usually regulated in the room to meet the requirement of the owner which is usually 0.3 Air Changes. The system is also able to supply the required amount of air to areas where the owner usually spends most of his time.
  5. The mechanical system is usually quiet for the owner to not to be tempted to switch it off to minimize the noise.
  6. It does not obstruct other systems. For example, some of the fuel-fired systems. In such situation, the system which might bring about a high negative pressure in the room that can lead to destruction of the owner properties is avoided.
  7. Mechanical ventilation system does not lead to positive pressure within the room. This will bring about some humid air via the building envelope from the room. So it does not obstruct the building envelope.

Advantages of Mechanical Ventilation

  1. There is no dependency on outside weather conditions despite the noisy environment.
  2. Heats can be extracted from the exhaust air and be used in preheating the pure air supplied.
  3.  Mechanical supply of air can also be used in pre-cooling and preheating the air supplied.
  4.  Air can easily be cleaned by an air filter or it may be supplied from a site of a building which is clean.
  5.  The air supplied can easily be humidified and dehumidified.

Demand-Controlled Ventilation

A system that operates when required and also when needed only, is usually controlled by an arrangement of sensors that is one for moisture and the other one is for the pollutant that the ventilator might produce, this also involves carbon monoxide, volatile organic component, formaldehyde and carbon dioxide. The ventilator can distribute air until all the sensors can be realized whether it’s above or below the safe level, and if it is above, then the ventilator can work.

In most cases ventilators are controlled by dehumidistats where it shows that the humidity in the room is at safe level. The skyscrapers use carbon dioxide as the main sensor used to control ventilators though nowadays it has spread to the residential areas. The more concentrated carbon dioxide is usually the best sign of reducing air quality. Most of printers and photocopiers usually emit carbon and ozone, for this purpose mechanical ventilation systems are installed. In many industries, these ventilations are also required to protect them for the impure air that is emitted. This helps the industries to protect both those who are the occupants internally and those who are outside externally to the environment.