1. AIR FLOW PATTERN:- For determination of air flow pattern, a titanium tetrachloride stick is burnt and placed in front of the AHU. The distribution of smoke is observed. It should be uniform.
  1. AIR FLOW VELOCITY AND CHANGES PER HOUR: For this test, the area of HVAC is divided into four hypothetical grids and the air velocity is measured at each grid and then the average air velocity (V) is calculated.

Calculate the Area (A in square feet) of each Air inlet as product of the  length and the width.
Calculate the Total Air Volume ( T in cubic feet per minute ) supplied in each zone, by using the formula :
T  = A x V
where  A  =  Area of particular Air inlet in square feet.
V  =  Average air velocity at particular air inlet in feet per minute.
Calculate the total volume of the room by multiplying length of room, breadth of room and height of the room.
Total air change is divided by total volume of the room will give the air change per hour.

  1. FILTER LEAK TEST: To check the leak test of the HEPA filter, a velometer is placed at the front of the AHU system and the air velocity is checked at all the corners. The air velocity should be within the higher limit of the HEPA filter. In case it is found to exceed the upper limit, a gas cut (silicon) is used to decrease the leakage.
  1. PARTICLE COUNT:- A particle counter is used to conduct the test. Particle count is taken before the operation as well as during the working condition. The particle count should be within the range as per the standards of Grade A, B, C, and D area.
  1. VIABLE MONITORING: Viable monitoring is performed on daily basis by employing the swab test and using nutrient agar medium for the incubation of microorganisms. The different media plates are exposed in every manufacturing section including the reverse air duct of the HEPA filter at the back of the cubicle. The microorganism count should be within the range and if it is found out of specification for consecutive two times, an effective corrective and preventive action is taken.
  1. FILTER INTEGRITY TEST (DOP/PAO TEST):- The HEPA filter integrity is tested by generating a PAO aerosol by an aerosol generator at 20psi air pressure and allowing the upward flow of the aerosol. The 100% upward flow of the aerosol is ensured and then the receptor probe of the HEPA is monitored to know the amount of the aerosol reversed. It should not exceed the higher limit of the HEPA filter.
  1. FRESH AIR DETERMINATION:- The fresh air intake is observed at the inlet on the fresh air dumper. The total air change is calculated.The intake fresh air is divided by the total air change in the room and multiplied by 100 to obtain the percent fresh air intake on each cycle by the HVAC system in all the individual rooms.
  1. TEMPERATURE AND HUMIDITY UNIFORMITY TEST:-The uniformity of temperature and humidity are monitored by using a calibrated thermometer and manometer, respectively. The two parameters are monitored on daily basis, documented in the format and stabilisation is ensured within the specified limit.
  1. RECOVERY :- In this, the humidity and temperature are checked at the off position of the HVAC system. Then the humidity is increased to 75% and temperature to 40°C and again the temperature and humidity are measured after switching on the HVAC system, and the time required to stabilise the temperature and humidity is noted.
  1. PRESSURE DIFFERENCE:- It is calculated by using the manometer attached at the walls of the adjacent area. The pressure difference is generally kept between 5 – 20 mmHg pressure.


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