The ventilation system is mainly classified into two types depending upon the movement of air flow inside the work place. These two kinds have their own advantages and disadvantages. The two kinds are – dilution type ventilation system and the local exhaust type ventilation system. The local exhaust system is a bit costly system than the dilution ventilation system.
- As the term says ‘dilution’, the air inside the working area is mixed with the fresh air in order to make the contaminated air less polluting to the people inside the working area.
- This type of ventilation system is generally used when the working area is less and the polluted air is not chemically toxic.
- The working of this type is very simple. It uses a simple exhaust fan which directs the air to flow from one direction to another direction i.e. from the more polluted side of the work place to the less polluted side.
- One of the limitations of the dilution ventilation system is that the contaminants are not completely removed from the work area. This may have an effect on the people when they have long term exposure to the moderately contaminated air.
- So, it may not be effective in industries which deal with poisonous gases. As the system uses a simple exhaust fan to blow the air, it may not direct the air completely inside the work area.
- It also requires large amount of fresh air that has to be circulated inside the work area.
Local Exhaust Type
- In local exhaust type, the ventilation system is fixed at the beginning of the source of contaminated air where it completely sucks the polluted air and discharges it outside.
- In this type, the contaminated air is replaced with the fresh air. It uses a series of tubes, a hood which absorbs the contaminated air, an air cleaner, and a couple of fans.
- Local exhaust type is usually used when the contaminated gases are more toxic that may cause series of health problems with minute exposure to the gas. In most of the pharmaceutical industries this kind of ventilation system is used in order to remove the contaminated air in the work place.
- Some limitations of this type are that it is of high cost and maintenance should be done regularly.
- A skilled person is required for cleaning the parts of the system and for its maintenance.
- As the parts of the system are exposed to the toxic gases, they may get corroded. Installation is a bit difficult when compared to the dilution type.
Depending on the work place and the level of contamination in the industry, a right ventilation system has to be installed.