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Engineering ToolBox > Garage Ventilation
In a garage or workshop where exhaust gases like Carbon Monoxide (CO) and NOx from vehicles are very dangerous, proper ventilation of the area is very important.
Garages or workshops with floor areas more than 500 ft2 (50m2) should always have mechanical ventilation with fans. Smaller garages can have natural ventilation with evacuation of air through ducts with larger area than 0.2% of the floor area.
As a general rule of thumb the minimum
The fresh air supply to the garage can be calculated as
Q = n V (1)
where
Q = total fresh air supply (m3/h)
n = required air changes per hour (h-1)
V = volume of the garage (m3)
The fresh air requirement in a garage can also be calculated using the CO emission from the vehicles in the garage.
qCO = (20 + 0.1 l1)c1 + 0.1 c2 l2 (1)
where
qCO = CO emission (m3/h)
c1 = capacity of parked cars in the garage
l1 = mean driving distance for cars in the parking garage
c2 = numbers of cars driving through the garage
l2 = mean driving distance for cars driving through the garage
The required fresh air supply can be estimated with
Q = k qCO (2)
where
Q = required fresh air supply (m3/h)
k = application coefficient
The application coefficients used are
The fresh air supply to a storage garage with 10 cars, floor area 150 m2, volume 300 m3 and a mean driving distance for the cars of 20 m, can be calculated as:
Using an air change requirement of 4 per hour the required fresh air supply can be calculated as
Q = 4 300 (m3/h)
= 1200 m3/h
The CO emission can be calculated as
qCO = (20 + 0.1 20)10
= 220 m3/h CO
The required air flow
Q = 2 220 (m3/h)
= 440 m3/h air
The fresh air supply should be 1200 m3/h.
The fresh air supply to a repair garage with 10 cars, floor area 150 m2, volume 300 m3 and a mean driving distance for the cars of 20 m, can be calculated as:
Using an air change requirement of 4 per hour the required fresh air supply can be calculated as
Q = 20 300 (m3/h)
= 6000 m3/h
The CO emission can be calculated as
qCO = (20 + 0.1 20)10
= 220 m3/h CO
The required air flow can be calculated as
Q = 4 220 (m3/h)
= 880 m3/h air
The fresh air supply should be 6000 m3/h.
Local regulations and codes must always be adapted. Is important not to underestimate the traffic in the garage and the required air flow.
A typical solution for smaller garages is shown below.
The fresh air is supplied through openings in the outside wall. Polluted air is evacuated through openings close to the floor and the roof.
In larger buildings and garages it is common to use air from the ventilation systems in the surrounding buildings as fresh air supply to the garages.
Air with room temperature (or the temperature after the heat recovery unit) is supplied to the garage. Polluted air is evacuated through openings close to the floor and the roof.