The fresh air supply system is often mentioned as one of the effective methods for removing dust and harmful substances. So, what is the fresh air supply system? What are the standards for fresh air supply? The following article will address these questions and related issues surrounding fresh air.
What is Fresh Air? The Importance of Fresh Air Supply?
Simply put, fresh air is outdoor air that is not polluted. In fact, fresh air plays a crucial role in balancing life and ensuring human health.
According to biological principles, humans inhale O2 and exhale CO2 into the environment. If there is only CO2 in the air, humans will feel extremely uncomfortable and fatigued; thus, fresh air is needed to provide sufficient O2 for comfort. This is especially important in air-conditioned environments or closed spaces where natural air exchange is limited. To ensure an adequate supply of O2 for gas exchange, a certain amount of fresh air is essential. In many cases, a lack of O2 can lead to dizziness, nausea, and even pose a danger to life.
Fresh Air Supply System
Typically, there are two methods for supplying fresh air: forced ventilation and natural ventilation. Each type has a different structure and operating principle. Specifically:
Natural ventilation primarily uses ventilation openings or air louvers.
Forced ventilation, on the other hand, commonly uses fans to expel air rich in CO2 to the outside. This air is replaced with O2-rich air. To ensure the accurate supply of fresh air, calculations must be made according to specific standards, such as TCVN.
Based on the TCVN 5678:2010 standard, which clearly defines fresh air supply standards for various types of commercial, residential, and industrial buildings or specific construction areas, the minimum fresh air requirement is 20m3/person/hour. Therefore, the design of the fresh air system must adhere to and ensure the accuracy of this standard.
The Operating Principles of the Fresh Air Supply System
The fresh air supply system is designed to perform the following main tasks:
It quickly expels harmful substances and impurities contained within the room to the outside. Specifically, in living spaces, the harmful substance is primarily CO2. Additionally, it also serves to remove excess moisture and heat. Typically, we use ceiling exhaust fans or wall-mounted exhaust fans for these two tasks. Along with that, the system provides the necessary oxygen for human activities.
In spaces that are not very large and have many people, with the doors closed, the amount of air may not be sufficient to maintain and meet the consumed air volume. At this point, we need to use a fresh air supply fan. Conversely, in spaces with fewer people where the doors are not tightly closed, we can use exhaust fans, as clean air will quickly fill the space due to pressure differentials.
The fresh air supply system helps expel harmful substances contained within the room to the outside.
What is the Adequate Standard for Fresh Air Supply?
As presented in the previous section, the amount of fresh air supplied depends on the requirements and specific scope of each construction project. Some common arrangements for apartments and office buildings include:
- Only fresh air supply, single-line air system
- Only exhaust air, single-line air system
- Two-line ventilation system combined with fans.
According to Vietnamese standards, the amount of fresh air supplied to air conditioning systems must ensure at least 10% of the total circulating air flow, with a minimum of 20m3/h/person. To determine how many people can be accommodated per square meter, refer to the TCVN from the Ministry of Construction. In cases where fresh air is supplied using mechanical methods, it is best to supply it into the return air ducts. Besides calculating the system and fresh air supply standards, it is also essential to calculate the design of duct systems and select air outlets. This is an important step after determining the necessary ventilation flow rate. Calculating duct systems, identifying air outlets, and the number of ducts connecting to the equipment will help determine the flow rate through each outlet, as well as the dimensions of ducts and outlets.
In general, calculating the fresh air supply system is not as complicated as you might think. With just a few simple steps, you can calculate the required amount of fresh air. You can also seek assistance from reputable and capable units.
