This is how we execute lift lobby and staircase pressurization projects

In office buildings, hotels, hospitals, and many other high storey buildings, the lift lobby and staircase areas are designated for fire fighting or escape path purposes respectively. Therefore, pressurization is mandated to prevent smoke from entering these areas. In other words, pressurization is a technique to create a positive pressure with the sole objective of stopping the entry of smoke in designated areas such as in the lift lobby or staircase. As per the codes and laws, buildings should incorporate fire precautions and smoke control measures in their design. The objective is to allow people to use the staircase in case of a fire breakout. At the same time, service lifts should be available for use for the fire fighting team. And this is achieved by the method called ‘Pressurization’. In case of fire breakout or smoke generation in any given building, the positive pressure is created through external sources in the lift lobby and staircase. This external pressure is created by switching on the high volume and high static pressure tube axial fans that are ideally located on the terrace of the given building. As soon as the fire alarms are triggered, the building management system (BMS) activates and switches on the tube axial fans located on the terrace to generate positive air pressure in the staircase and lift lobby areas. Separate fans are used for staircase and lift lobby areas. The desired air volume of these fans is calculated by measuring the staircase or lift lobby area and the total numbers of floors in the building.

Design

The design is at the heart of any pressurization project. The first step in the design process is to calculate the lift lobby or staircase volume. This is done by measuring the length, width, and the height of the lift lobby or staircase. This way, we have estimated the correct volume in cubic feet. The next step is to estimate the leakages that may take place because of gaps or openings in these areas. The third step is to calculate the desired positive pressure that is needed to stop the smoke from entering the lift lobby or staircase. The desired pressure generally falls between 35 Pa to 50 Pa. After estimating the area, leakages, and positive pressure, the airflow rate in CFM (Cubic Feet per Minute) is calculated. This airflow rate in CFM is multiplied by the number of floors in the building to accurately calculate the air volume of the tube axial fan. For example, if the airflow rate in CFM for each lift lobby or staircase area comes out to be 2500 CFM, and the building has 15 floors in total. Then, the tube axial fan with an air volume of 2500 x 15 = 37500 CFM would be needed to pressurize the lift lobby. Likewise, another tube axial fan with an air volume of 37500 CFM would be needed to pressurize the staircase zone in the building.

A duct line passing through all the floors is connected to the tube axial fan. From this main duct line, branches are carved out to discharge the calculated air volume to each of the floors in the building. A grill is then installed on each of the branches to allow for the airflow at the estimated pressure. Now, what should be the shape and size of the main duct line? This is again calculated by the total available air volume on each floor and the desired pressure on each floor. For example, if there are a total of 15 floors in the building, and the air volume capacity of the tube axial fan is 37500 CFM, then, on the 15th floor, the total available air volume is 37500 CFM. Now, 2500 CFM would be discharged on the 15th floor through the branched duct. Therefore, total available air volume on the 14th floor would be 35000 CFM. This way, total available air volume is calculated for each  and every floor. This availability of air volume along with the desired pressure determines the shape and the size of the main duct line.

Likewise, the shape and size of a branched duct is calculated. Since, the available air volume for each and every branched duct is 2500 CFM, and the desired pressure is 35 to 50 Pa, accordingly the dimensions of a branched duct are calculated.

The tube axial fan should be connected to the nearest BMS compatible panel in order to switch on or off the fan based on the fire alarm trigger.

This is how the design of a typical pressurization project is made.

Installation

Even after the design has been perfectly drawn, the installation has its own challenges. The main duct line passes through a shaft. And that shaft comprises civil concrete work and chequer plate on each and every floor. Based on the main duct line dimensions that were estimated in the design phase, the concrete and the chequer plate needs to be cut. This is a labor intensive process. Sophisticated tools and machinery are used to cut the concrete and the chequer plate. After cutting the concrete and the chequer plate, the main duct line is installed. From the main duct line, branches are carved out for each and every floor. And thereafter, grills are installed on each and every floor. A plenum is ideally inserted between the main duct line and the tube axial fan. This is done to eliminate the vibrations in the main duct line. Once the installation has been completed, the pressurization project is tested for 2-3 weeks. Testing is extremely important to ascertain that the system works well in case of a fire breakout in the future.

TheSmartHVAC is working with leading commercial real estate developers across India for such pressurization projects.

Whether it’s an office building, or a hospital building, or a hotel building, or any other commercial high storey building, TheSmartHVAC team emphasizes on the design in order to make sure that the building complies with the fire safety codes and laws. Building owners, property managers, facility managers from Chennai, Pune, Mumbai, Bengaluru, Gurugram, Noida, Ghaziabad, Hyderabad, New Delhi, Kolkata, and other parts of the country can reach out to TheSmartHVAC for pressurization projects. The team will deliver the end-to-end pressurization project from design to installation.

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