When you intend to purchase a ventilation fan, do not simply take any fan.
All spaces—bathroom, kitchen, office, or bedroom—should have the appropriate fan size to keep the air fresh and comfortable.
This is the list of the main aspects to consider when choosing one.
1. Airflow (CMH / CFM)—The Respiratory of Ventilation.
Airflow refers to the volume of air the fan can move in a minute.
It is taken in CFM (Cubic Feet per Minute) or CMH (Cubic Meters per Hour).
The more airflow there is, the more air is replaced and the faster the ventilation.
How to Calculate:
Formula:
CFM=L×W×H×ACH/60- L, W, H = Room Length, Width, Height (in feet)
- ACH = Air Changes per Hour (depends on room type)
| Area Type | Recommended ACH |
|---|---|
| Private Toilet | 10–15 |
| Kitchen | 15–30 |
| Bedroom | 5–10 |
| Office | 6–10 |
| Gym | 15–20 |
| Basement | 6–12 |
Example:
Bathroom 8×6×9 ft →
CFM = (8×6×9×10)/60 = 72 CFM → choose fan ≥ 80 CFM (like AF100P).
In the case of regular rooms: approximately 1 CFM/ft.
In humid or smoky places (such as kitchens or bathrooms): 1.5 to 2 CFM/ sqft.
Other Examples:
A 100 sq. ft. The bathroom should have approximately a 100 150 CFM fan.
It requires approximately 250 to 300 CFM for a 150 sq. ft. kitchen.
A 400 sq. ft. living room can require 400-500 CFM in case it is closed with fewer windows.
Tip:
This is because when you use ducts or false ceilings, the resistance to the airflow is higher, which means you need to add 10-20% to the airflow requirement.
2. Static Pressure.
There is also the concept of the static pressure, pressure that refers to the capacity of the fan to press air through barriers such as ducts, bends, filters, or grilles.
It is measured in mmHg or Pascal (Pa).
In case of low static pressure, the fan will have a hard time moving air in a duct system.
Examples:
In case the fan is directly mounted on the wall, a low static pressure (10-20 mmH₂O) suffices.
In case air travels via 3-5 meters of duct, you will require a medium-pressure fan (30-40 mmAq).
High static pressure (60-80 mmH₂O) fans should be used when dealing with long ducts or commercial ventilation.
Tip:
Never overlook the static pressure rating where your fan is to be connected with ducts, as this makes the difference in the right amount of air flowing at the duct outlet.
3. Noise Level (dB)—Comfort Without Disturbance.
The noise level lets you know how noisy or how not noisy the fan is.
It's measured in decibels (dB).
Guidelines:
Less than 35 dB - Must be quiet (good in bedrooms or offices)
35-45 dB - Moderate noise (suitable in kitchen or bathrooms)
The sound above 50 dB - Loud and inappropriate in quiet places.
Example:
When putting up a fan in a bedroom or a study room, you must always select one that has a low noise level (Less than 35 dB).
A 40-45 dB fan will suffice in a kitchen or toilet since the surroundings are noisy.
Tip:
Select fans of EC motor or backward-curved blade design—they are less noisy and smoother.
4. Energy Consumption—Energy Saving Matters.
Do check the motor type and wattage of the fan.
A decent ventilation fan must have a high airflow and produce less power.
Examples:
An average AC motor fan can use approximately 60 watts.
A comparable airflow EC motor fan can only consume 30 watts - it can save up to 50 percent of electricity.
Assuming that you are running the fan 10 hours a day, the EC motor conserves approximately 100 units of power per year, which translates to a lower electricity bill.
Tip:
In case of continuous ventilation (offices or commercial spaces), EC motor fans should always be preferred.
5. Fan Type—Match with Installation Area
Each of the areas has a varying ventilation requirement. Select the type of fans:
Axial Fan:
Moves air straight in and out.
Short duct distance, ideal when installed in the wall or windows.
These are usually installed in bathrooms, toilets, small cabins, or kitchens.
Centrifugal Fan:
The air comes in at the center and is given out at 90 degrees.
Long ducts and increased duct pressure.
Applied in restaurants, commercial kitchens or industrial settings.
Inline Fan:
Fitted on the duct or ceiling.
Has a clean appearance and quiet working.
Office, best meeting rooms, or a room that has false ceilings.
Tip:
Never use the wrong type of fans when trying to install it in a wall, ceiling, or duct.
6. Material / Durability: To promote Long Life Performance.
The quality of its building is important, particularly in humid or outdoor locations.
The fans are to be rust-proof and resistant to corrosion.
Professional metal housings, ABS plastic, or powder coating are preferable.
In coastal or industrial conditions, opt to use IP-rated motors as an added protection.
Example:
Ordinary fans can be corroded by moisture in a bathroom, so it is better to have a plastic or a coated metal fan.
A metal centrifugal fan is required in a restaurant kitchen to deal with grease and heat.
7. Intelligent Controls & Functionality - To be convenient.
New ventilation fans have handy intelligent features:
Humidity sensors: The Fan automatically activates when the humidity increases.
Timer control: The Fan operates for several minutes following the switching of the light.
Control of speed: Control airflow according to your demand.
Motion sensor: Activates when one enters the room.
Example:
In a bathroom, a timer fan makes sure that all the humidity and odor are removed even when you are gone.
Speed control assists in balancing working and off-office ventilation levels in an office.
Final Advice
Before you buy, always:
Measure your room area (sq. ft.)
Divide the airflow (CFM) needed.
Check static pressure, level of noise, and energy consumption.
Select the appropriate type of fan to install.
The proper choice of a ventilation fan guarantees fresh air, low odor, low humidity, and energy-saving, which would be reliable in the long term.
