SOP for Measurement of Air Velocity and Calculation of Air Changes per Hour

1.0 OBJECTIVE

To lay down the procedure for measurement of air velocity and calculation of air changes per hour for classified areas.

2.0 SCOPE

This SOP shall be applicable for classified areas and laminar air flow.

3.0 RESPONSIBILITY

Officer /Executive/Assistant Manager

4.0 ACCOUNTABILITY

Head of Engineering

5.0 PROCEDURE

5.1 Ensure that air handling unit is “ON” of that area.
5.2 Measure the hood /grill size and calculate the area of the hood / grill in sqft.
5.3 In case of terminal HEPA filters place the calibrated anemometer 6 inches away from the grill at different locations and measure the air velocity in feet per minute.
5.4 In case of diffusers place the calibrated anemometer at the bottom face of the hood at different locations and measure the air velocity in feet per minute.
5.5 Calculate the average air velocity of the five locations.
5.6 Calculate the air quantity in CFM by multiplying the area with average air velocity.
5.7 Repeat the Step 5.2 to step 5.5 for all supply air diffusers/ grills available in the room.
5.8 Calculate the total air quantity in CFM inside the room.
5.9 Calculate the air changes per hour.
5.10 Record the observations in a format of measurement of air velocity and calculation of air changes.
5.11 The frequency for measurement of air velocity and calculation of air changes shall be once in a year for classified areas.
5.12 The frequency for measurement of air velocity for laminar air flow shall be once in a six months and shall be done by an external agency.
5.12.1 The velocity measurement shall be carried out as per schedule shown.

5.13 ACCEPTANCE CRITERIA

5.13.1 The measured air quantity shall not be less than the designed air quantity and the calculated air changes shall not be less than the designed air changes per hour.
5.13.2 Average air velocity for laminar air flow shall be 90 +/- 20%
5.14 If the acceptance criteria don’t meet then take the necessary corrective actions and repeat the step 5.3 to step 5.9.

6.0 ABBREVIATIONS

6.1 SOP: Standard Operating Procedure
6.2 CFM: Cubic Feed per Minute

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