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Why is it Compulsory to Use Exhaust Fans

Posted by Vikram Singh on

Just like a human body, the interiors of a building also do need to breathe well; otherwise it becomes a gas house of stagnant air, where carbon and bacteria building up makes the space hazardous for the inhabitants.

Exhaust Fans Removed carbon and bacteria

But the question arises, are the buildings in the most congested cities of India, ventilated enough to allow fresh air to enter inside.  This question has a straightforward answer ‘no’. The buildings in Delhi, Mumbai and Bangalore like cities are so congested and overcrowded that your neighbor can easily tell you which dishes you cooked overnight for your guests.

In this scenario, it becomes important to replace stale air with fresh air; otherwise, the air inside your house will become susceptible to stagnant air and make it more polluted than the air people in Delhi are breathing this time.

use of exhaust fans

The use of exhaust fans in buildings solves this problem to a very large extent.  There are exhaust fans for kitchen and exhaust fans for bathroom which reduce the foul smell and drive out the moisture from the kitchens to keep things fresh and healthy.   

Exhaust Fans are widely used in the households, offices, hospitals, hotels, restaurants and in other commercial and residential buildings.

 Why is it compulsory to use exhaust fans in kitchens and bathrooms?

use exhaust fans in bathrooms and Kitchen

  1. Many of you may have heard about Sick-building syndrome, it is the direct outcome or we can say fallout of the buildings that lack proper ventilation. The air inside the poorly ventilated houses remains often loaded with health hazardous substances that cause various health issues. According to a recent report of WHO, more than 50% remodelled and new construction is plagued by the poor indoor air quality.
  2. The irony about the houses in Delhi, Mumbai and Bangalore like metropolitan cities is you don’t have scope to renovate and carve out more ventilating windows from the walls. Because the buildings are built adjacent to each other with walls in common. There is just one way to keep the air clean inside modern-day buildings that is using exhaust fans. Though they can be installed anywhere in the house to keep the air inside fresh, they are mainly used in the bathrooms and kitchens
  3. The exhaust fans are mostly used in kitchens and bathrooms, the reason is if the air in the bathrooms and kitchens is not purified, it affects the overall quality of the air and the foul smell spreads in the entire home and its surroundings. 
  4. Not just odours, they also remove the moisture in the air to keep your interiors dry and fresh. Otherwise, the humidity in your house will prompt the growth of bacteria, fungus and moulds in your house that gives rise to infections. The fungus, bacteria and moulds cause allergy, food poisoning and serious skin problems.
  5. Not just infections, the growth of moulds, bacteria and fungus in your house will cause a serious damage to the furniture, windows and doors. Thus bathroom and kitchen exhaust fans are just essential to install in the kitchen and bathrooms of every building be it a residential complex or a corporate office.     

 Types Of Exhaust Fans

Types Of Exhaust Fans

There are many types of exhaust fans for kitchens and bathrooms available in the market based on the size, orientation, CFM number and Static pressure. We will discuss here only the major ones.

Types Of Exhaust Fans Based On The Shape And Design

  1. Impeller fans: The blades of the Impeller fans are just like the propellers of a plane.
  2. Blower fans: Blades of the Blower fans look like Hamster wheels hence often termed as squirrel cages. The Blower fans are considered more effective than the Impeller fans when it comes to doing the job of moving air.

 Types Of Exhaust Fans Based On CFM Number

  1. Belt drive: Belt drive exhaust fan models are considered just apt for air volumes surpassing 2,000 CFM and static pressure above 0.50. Its adjustable pulleys enable both CFM and fan speed to be adjusted by more than 25%. The high-temperature fans above 122 F0 are maximum belt driven models of kitchen exhaust fans
  2. Direct Drive: Direct Drive is a very simple model of exhaust fans kitchen available in the market. They are mostly used in households for low volume (2,000 CFM or less) and static pressure below 50C. It is totally opposite to belt-driven exhaust fans as far as its features are concerned.
  3. Propeller: The propeller is an economical model of exhaust fans for kitchens which is capable to blow air volumes above 5,000 CF but static pressure below 0.50C. Its motors are mounted in the airstream which makes it possible to clean air at less static pressure and low temperature. 
  4. Centrifugal: On the other hand, the centrifugal fans show more efficiency at higher static pressures an make very less noise than the propeller fans. Some Centrifugal exhaust fan models are specially designed with motors mounted out of the airstream to ventilate highly contaminated high-temperature

 How To Choose A Right Exhaust Fans For Kitchens & Bathrooms 

How To Choose A Right Exhaust Fan

It is not necessary that all exhaust fans for bathrooms and kitchens will have same features and functions. There are some exhaust fan models on the market that are used just for some specific functions. Among the key variables that determine the quality of the exhaust fans for kitchens & bathrooms are the model and the volume of air it is able to blow in per unit of time.

 In addition, the factors like Static Pressure (SP) and Noise an exhaust fan produces (sones) taken into consideration while purchasing an exhaust fan for kitchen or a bathroom.

Here are some exhaust fan specific guidelines that will make it easy for you to select the best quality and effective exhaust fans for kitchen & bathroom at home and Offices.

  1. Fan model

Fan model is one of the most determined parameters when it comes to select an exhaust fans for kitchen and bathroom. You should only select a particular model of an exhaust fan. The reason is that there are exhaust fans available in the market that supports a diverse number of features. Each one of them has its own specific uses. An exhaust fan of one model can’t be used everywhere.

If it is a kitchen-specific exhaust fan, then you can use it only in the kitchen, it will not prove effective to purify the air in big commercial buildings.

You will need to find a one for your bathroom or kitchen that is just apt for them in terms of electricity consumption, air volume and snag proof.

  1. Fan location

The location is one more determining factor that one needs to take into consideration before purchasing an exhaust fan. Some exhaust fan models are specifically designed to mount on a roof straight under cloud. This model of exhaust fans can’t be used for kitchens and bathrooms. Though the components of the fan remain same they differ in their orientation.  Some exhaust fan models are designed to fit in a gap in the wall or in a duct.

  1. Survey the structure of the building

Which model of exhaust fan you need will depend on the air flow to be blown out.   It is obvious, in a factory; you need exhaust fans that have the ability to blow high volumes of air in less time.  And in case of the kitchen, you will need an exhaust fan of relatively less strength.  So,  just before purchasing an exhaust fan, just survey the structure of the building and see how the air can be blown out, you will get an idea where you should place the fan.

  1. Cubic Feet per Minute (CFM)

The third most crucial factor to determine which exhaust fan you need for your residential or commercial building is Cubic Feet per Minute (CFM) because it is the amount of air that will ultimately decide which type of exhaust fan you need for your kitchen or bathroom. An exhaust fan of a specific range will clear the air only in the corresponding areas while as there are the high range exhaust fans which clear the air even outside of their specific range.

  1. Climate of the place

The climate of the place will also decide how much CFM exhaust fan you will need for your building. For places where the climate is hot and humid, you will need an exhaust with less CFM Value so that it is able to change air quickly.  For areas with a moderate climate, you should select an exhaust fan with high CFM number value.

  1. Static pressure

The static pressure is another metric to determine which model of exhaust fan will be suitable for your building. It is measured in inches of water gauge. The pressure difference between the duct and the atmosphere causes the water level in the manometer legs to rest at different levels. This difference is called as the static pressure. The air velocity in the ductwork, duct length and duct turns will determine the static pressure that an exhaust fan has to overcome.

  1. Close as possible to the source

The large bathrooms in commercial buildings, hospitals, hotels, schools, colleges and universities etc, you should select an exhaust fan more in size and power and place it as close as possible to the source of moisture or odour.

Features Bathroom & kitchen exhaust fans should possess

 Here are some of the features that a bathroom or kitchen exhaust fan should possess:

  1. 25 L/S or 50 CFM

The exhaust capacity of a fan is measured in litres per second or Cubic feet per minute (CFM). A normal bath needs an exhaust fan that is able to draw at least 25 L/S which is equivalent to 50 CFM’s. If you will select a poor quality fan for your bathroom, it won’t be able to exhaust enough air and will make enough noise for regular use.

  1. Works in wet conditions

Select an exhaust fan that works in wet conditions otherwise; it will get damaged in no time.

  1. Produce No Or Very Less Noise

Noise is one important factor that determines the quality of an exhaust fan because many people don’t like a noisy fan.  Exhaust fans are labelled as quiet or low noise.  The HVI rating also indicates is the fan noisy or quiet. 

  1. Has less tendency of attracting dirt

The electric fans create static electric currents which tend to attract dirt particles just as the magnet does with the lighter iron objects. This dirt on the fan blades encourages mould and bacterial growth and the air moment gets restricted. Select a fan that has less tendency of attracting this dirt.  And clean the fan by pulling down the grill.

Back-drafting and its dangers

When the fan is off, the wind loads or stack effects can push external polluted air into the bathroom or kitchen. The phenomenon is called backdrafting.  Backdrafting at times can be very dangerous because it can bring dangerous combustion exhaust gases into the house. Backdrafting occurs mainly when the exhaust fans are placed close to the chimneys in factories.   So always take care backdrafting don’t occurs.


The exhaust systems you often see installed in the big buildings consist of ducting, exhaust fan and an exterior hood.  The concept of Central Exhaust System is solely based on exhaust fans which draw the moisture and odours from the several rooms of a building using a network of ducts. In today’s world it is more than mandatory to use an exhaust fans for kitchens & bathrooms. In fact, one should use them for every room to get rid of the polluted air from the interiors of a house. The exhaust fans are not costly. The exhaust fan price starts from just 500 Rs.  So make an investment today, breathe fresh air and live healthy forever.

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