Car Park Ventilation System

Introduction

A car park ventilation system is designed to ensure air quality and safety in parking structures by controlling the buildup of vehicle exhaust gases, ensuring proper airflow, and maintaining safe oxygen levels. Ventilation in car parks is important to prevent the accumulation of harmful gases like carbon monoxide (CO) and nitrogen dioxide (NO₂) and to keep the air fresh for drivers and pedestrians. Here’s a simple explanation of how it works, broken down into key topics:

Purpose of Ventilation in Car Park

1. Ventilation helps to remove pollutants from vehicle emissions, such as carbon monoxide, hydrocarbons, and nitrogen oxides, which can build up in enclosed spaces.
2. Proper ventilation ensures there is enough fresh air for people to breathe and helps prevent dangerous situations like asphyxiation or suffocation from lack of oxygen or high levels of toxic gases.
3. It helps maintain a comfortable environment by reducing the build-up of heat and humidity, especially in underground or enclosed parking structure.

Types of Car Park Ventilation Systems

1. Natural Ventilation

1. Relies on natural forces like wind and temperature differences to circulate air. Vents, openings, and ducts are placed in the car park's structure to allow air to flow through.
2. Low cost and low maintenance.
3. Less effective in large, enclosed spaces or areas with low airflow.

2. Mechanical Ventilation

1. Uses fans, blowers, and exhaust systems to actively circulate air. This system is more controlled and effective than natural ventilation, especially in multi-story or underground car parks.
2. Types of Mechanical Systems:

1. Exhaust fans is Used to expel polluted air out of the car park.
2. Supply fans is Bring in fresh air from the outside.
3. Mixed systems are A combination of exhaust and supply fans to create a balanced airflow.

Hybrid Systems

Combines natural and mechanical ventilation means Mechanical ventilation is activated when natural airflow isn’t sufficient, such as during peak times or in more enclosed areas of the car park.

Key Design Considerations

1. Air Changes per Hour (ACH)
   1. ACH measures how often the air in the parking structure is replaced in one hour. For example, an ACH of 10 means the air is completely replaced 10 times in one hour.
   2. Depending on the size and type of the car park, typical ACH values range from 3 to 10. Higher ACH is required for car parks with more vehicles or higher levels of pollutants.
   3. Local codes and standards (like those from the NFPA or ASHRAE) often define minimum ACH requirements for car parks.
2. Pollutant Control
   1. CO (Carbon Monoxide) is a toxic gas produced by car engines. It is one of the main targets of a car park ventilation system.
   2. NO₂ (Nitrogen Dioxide) is a Another harmful gas from vehicle emissions that needs to be removed.
   3. Particulate Matter (PM) is a Dust and particles from exhaust fumes or tires that the system helps mitigate.
3. Ventilation Rate Calculation
   1. To determine the number of fans and the size of ducts, engineers consider the volume of the car park, the desired ACH, and the amount of pollutants expected.
   2. Ventilation requirement formula: 

Ventilation System Components

1. Exhaust Fans
   These remove polluted air from the car park. They are placed at high points in the structure, often near the ceiling, to expel hot, contaminated air.
2. Supply Fans
   These bring in fresh air from outside the car park to replace the exhausted air. They are usually placed near lower levels or side walls.
3. Ducting
   Ducts distribute the fresh air into the car park and evacuate the polluted air. These can be vertical or horizontal, depending on the layout.
4. Air Vents
   1. Inlet Vents Allow fresh air to enter the car park from outside.
   2. Exhaust Vents Allow polluted air to exit the car park.
   3. Vent placement is key to ensuring that air circulates effectively, and pollutants are removed.
5. Control Systems
   1. CO and NO₂ sensors are installed to monitor the air quality in real-time. The system adjusts the fan speed or operation based on pollutant levels.
   2. Timers and Automated Controls: In some systems, fans may be turned on or off based on traffic volume or time of day.

Ventilation Strategies

1. Demand-Control Ventilation (DCV)
   1. The ventilation system adjusts based on real-time data from sensors. For example, when more cars enter and exit, the system detects higher CO levels and increases ventilation accordingly.
   2. More energy efficient as it reduces the operation of fans when not needed.
2. Constant Ventilation
   1. The system runs continuously at a constant speed or rate, regardless of traffic or pollutant levels.
   2. Simpler and more reliable but can be less energy efficient.

Maintenance and Monitoring

1. To ensure the system works effectively, the ventilation system should be regularly inspected for blockages, dirt, or damaged components. Fans, ducts, and filters need periodic cleaning and maintenance.
2. Many modern systems come with automated monitoring, logging, and alert systems that can notify operators when ventilation is insufficient, or a fault occurs.

Energy Efficiency Considerations

• Fan Speed Control Modern systems use variable-speed fans that adjust speed based on air quality or car park activity, reducing energy consumption.
• Energy Recovery Some systems incorporate heat recovery mechanisms to use the exhaust air's thermal energy to pre-condition the incoming fresh air, saving on heating or cooling costs.

Summary

A car park ventilation system is vital for maintaining safe air quality by removing harmful vehicle emissions.

Key components include exhaust fans, supply fans, and ductwork. The system can operate on natural ventilation, mechanical ventilation, or a hybrid of both.

Proper design involves considering ACH, pollutant control, and ensuring the system meets regulatory standards.

Additionally, systems often incorporate demand-controlled ventilation for energy efficiency, and regular maintenance is crucial for long-term effectiveness.