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