Fresh Air CFM Calculation for Restaurants
Introduction to Fresh Air CFM Calculation
Fresh Air CFM (Cubic Feet per Minute) calculation is a crucial aspect of maintaining good air quality in indoor spaces, especially in environments like restaurants where a high density of people can quickly lead to poor air quality. Ensuring adequate ventilation is not only essential for comfort but also for health, as it helps in diluting indoor pollutants, reducing odors, and maintaining appropriate levels of oxygen and carbon dioxide.
Importance of Fresh Air CFM Calculation
In a restaurant setting, the importance of calculating the correct amount of fresh air cannot be overstated. The concentration of people in a confined space, coupled with activities like cooking, can lead to a rapid degradation of air quality. Proper ventilation ensures that fresh air replaces stale air, thereby maintaining a healthy and comfortable environment for both customers and staff.
Key Factors Involved in Fresh Air CFM Calculation
Calculating the required CFM for fresh air involves several key factors:

CFM per Person: This value indicates the amount of fresh air needed per person to maintain air quality. It varies depending on the type of indoor space and activity level.

Number of Persons: The total number of people expected to occupy the space at any given time. This is crucial as more people require more fresh air.

CFM per Square Feet: This value represents the amount of fresh air needed per square foot of space. It helps in determining the overall ventilation requirement based on the size of the area.
Formula for Fresh Air CFM Calculation
The formula to calculate the required fresh air CFM is generally given by:
Fresh Air CFM = (CFM per Person × Number of Persons) + (CFM per Square Feet × Area in Square Feet)
By using this formula, one can easily determine the amount of fresh air needed for any given space, ensuring that the indoor environment remains healthy and comfortable. The values for CFM per person and CFM per square feet can often be found in industry standards, such as those provided by ISHRAE (Indian Society of Heating, Refrigerating and Air Conditioning Engineers).
In the following sections, we will delve deeper into the stepbystep process of calculating fresh air CFM, provide an example calculation for a restaurant, and offer some concluding recommendations.
StepbyStep Guide to Fresh Air CFM Calculation
Calculating the Fresh Air CFM (Cubic Feet per Minute) is an essential task to ensure proper ventilation in a restaurant. Here is a detailed stepbystep guide to help you through the process:
Step 1: Understand the Formula
The formula to calculate Fresh Air CFM is as follows:
Fresh Air CFM = (CFM per person * Number of persons) + (CFM per square feet * Area in square feet)
Let's break down each component:
 CFM per person: The amount of fresh air required per person.
 Number of persons: The total number of people expected in the area.
 CFM per square feet: The amount of fresh air required per square foot of the area.
 Area in square feet: The total area of the space in square feet.
Step 2: Gather Required Values
Refer to the ISHRAE (Indian Society of Heating, Refrigerating and Air Conditioning Engineers) book to find the necessary values. The table in the book provides the following information:
 CFM per person for different types of areas (e.g., restaurants).
 CFM per square feet for different types of areas.
 Occupancy: The number of persons per 1000 square feet or 100 square meters.
For a restaurant, the values are typically:
 CFM per person: 7.5
 CFM per square feet: 0.18
 Occupancy: 70 persons per 1000 square feet
Step 3: Calculate the Area
Determine the area of the restaurant. For example, if the restaurant has a width of 30 feet and a length of 20 feet, the area calculation is:
Area = Width * Length
Area = 30 feet * 20 feet = 600 square feet
Step 4: Determine the Number of Persons
Using the occupancy value from the ISHRAE table, calculate the number of persons for the given area:
Number of persons = (Occupancy / 1000) * Area
Number of persons = (70 / 1000) * 600 = 42
Step 5: Plug Values into the Formula
Now that we have all the required values, we can plug them into the formula:
Fresh Air CFM = (CFM per person * Number of persons) + (CFM per square feet * Area)
Fresh Air CFM = (7.5 * 42) + (0.18 * 600)
Fresh Air CFM = 315 + 108
Fresh Air CFM = 423
Step 6: Conclusion
The calculated Fresh Air CFM for the restaurant is 423 CFM. To ensure comfortable ventilation, you can round up and use a fan with a capacity of approximately 500 CFM.
By following these steps, you can accurately calculate the Fresh Air CFM required for any restaurant or similar area. For more detailed information and values, always refer to the latest version of the ISHRAE book.
Example Calculation for a Restaurant
In this section, we will walk through a detailed example of calculating the Fresh Air CFM required for a restaurant. This process is crucial to ensure that the dining area is adequately ventilated, providing a comfortable and healthy environment for both customers and staff.
StepbyStep Calculation

Determine the Volume of the Space
To begin, we need to calculate the volume of the restaurant space that requires ventilation. This is done by multiplying the length, width, and height of the room.
Let's assume the dimensions of the restaurant are as follows:

Length: 50 feet

Width: 30 feet

Height: 10 feet
The volume of the restaurant is calculated as:
Volume = Length × Width × Height Volume = 50 ft × 30 ft × 10 ft Volume = 15,000 cubic feet


Determine the Air Changes per Hour (ACH)
The number of air changes per hour (ACH) required for a restaurant can vary based on guidelines and regulations. For this example, we will use a standard value of 15 ACH, which is typical for dining areas.

Calculate the Fresh Air CFM
The formula to calculate the Fresh Air CFM (Cubic Feet per Minute) is:
Fresh Air CFM = (Volume × ACH) / 60
Plugging in our values:
Fresh Air CFM = (15,000 cubic feet × 15 ACH) / 60 Fresh Air CFM = 225,000 / 60 Fresh Air CFM = 3,750 CFM
Ensuring Adequate Ventilation
The calculated Fresh Air CFM of 3,750 ensures that the restaurant's air is replaced 15 times every hour, which is adequate for maintaining good air quality and comfort levels. This helps in removing contaminants, controlling humidity, and providing a fresh and pleasant dining experience.
In conclusion, by following these steps, we can ensure that the restaurant is properly ventilated, contributing to the health and satisfaction of both customers and staff. For more detailed guidelines and recommendations, refer to the Conclusion and Recommendations section.
Conclusion and Recommendations
In conclusion, calculating the Fresh Air CFM (Cubic Feet per Minute) for a restaurant is a crucial aspect of maintaining optimal air quality and ensuring a comfortable environment for both patrons and staff. The stepbystep guide provided in this blog post outlines the process clearly, emphasizing the importance of using accurate values from reliable sources like the ISHRAE book.
Proper ventilation is essential to prevent the buildup of pollutants, control humidity, and provide a steady supply of fresh air. The example calculation demonstrates how to determine the required CFM based on the number of occupants and the area of the restaurant. By following the formula and using the values from the ISHRAE table, you can ensure that your restaurant meets the necessary ventilation standards.
Key Recommendations:
 Accurate Measurements: Ensure that you have precise measurements of your restaurant's dimensions and the expected number of occupants.
 Refer to Reliable Sources: Use the ISHRAE book or other trusted references to obtain the correct values for CFM per person and CFM per square foot.
 Regular Maintenance: Regularly check and maintain your ventilation system to ensure it operates efficiently and meets the calculated CFM requirements.
 Professional Assistance: Consider consulting with a professional HVAC engineer to verify your calculations and ensure your ventilation system is properly designed and installed.
By adhering to these recommendations, you can create a healthier and more comfortable environment for everyone in your restaurant. For further guidance and accurate values, refer to the ISHRAE book and other reputable sources in the field of HVAC engineering.