• Dhiraj Badane

Quick Guide to Carpark Ventilation

The use of ductless ventilation system [jet fans] for carparks has virtually become a default. It offers multiple benefits, in terms of space requirements, low cost and efficiency associated with its design, installation, operation & usage.


Covering details including, Purpose, Ducted v/s Ductless, Modes of Operations, System Components and Factors affecting ventilation rates.

Purpose: to dilute the level of toxic gases such as carbon monoxide (CO), oxides of nitrogen (NOx), presence of petrol / diesel fumes and smoke from engine exhaust. Maximum permissible CO concentration is 29 mg/m3.

Provide fresh air, removal of exhaust gases and smoke in case of fire.


6 Air-Change-Rate [ACPH] is defined by National Building Code [NBC] of India, to keep contaminants within acceptable hygiene limits.


Drawbacks of a ducted system:

  • Exhaust & fresh air fans have to be in operation throughout the day resulting in higher energy consumption

  • Polluted air removal is not efficient, if the duct layout is not proper; resulting in accumulation of polluted air pockets and improper extraction during fire

  • The duct height restricts maximum height for carparks & movement of vehicles


Benefits of a ductless system:

  • Lower power requirement & operating costs [upto 80% compared to ducted systems]

  • Improved directional control for jet stream giving greater smoke control in fire conditions.

  • Low noise, easy to handle during installation and ease of Operation & Maintenance



Modes of Operations: The logic will operate in three modes:

  • Zero Mode: ppm level of toxic gases is below 30. No equipment will be on.

  • Normal Mode: ppm level exceeds 30. In this mode, tube fresh air & exhaust air fans of respective zones will get operated as per 6 ACPH.

  • Fire Mode: ppm level exceeds 50. In this mode, tube fresh air & exhaust air fans of respective zones will get operated as per 12 ACPH.


Components of Ventilation System:


Carbon monoxide (CO) sensors: Designed for Demand Controlled Ventilation. The detector displays the parts per million (ppm) or CO in air.

CFD (Computational Fluid Dynamics) Analysis: The goal is to simulate & check flow patterns and visualise smoke / heat patterns.


Supply & Exhaust Air Fans: Fire Rated Axial Flow fans


Jet Fans: Jet Fans are an alternative to the ducted ventilation & give the basement a lighter feel by eliminating the use of ducts.


Factor affecting the Ventilation Rate (Q):

  • Numbers of cars in operation during peak usage (N)

  • Length of time of operation (Tm)

  • Car emission rate

  • Contaminant level criteria


#CGTechByte #Ventilation



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