Air handling unit (AHU) Qualilfication and Clean room classification

Air handling unit (AHU) Qualilfication  and clean room Classification : 

 Ensure the AHU is in switch ON.

 Switch ON the anemometer and allow it to some time for stabilization.

  Ensure that anemometer measuring unit is in FPM mode.

 To change the measuring unit mode, press the UNIT button till display shows FPM.

Take the readings at five locations at each filter as per below mentioned diagram.

           

V1                                    V2                      V5 V3                                    V4

•  Position the probe pointing towards airflow. Locate the probe approximately 1/6 diagonal distance and measure velocities from each corner.For clean room measurement shall be taken at a distance of 150 mm from the filter face. Take the readings after stabilization or take the average reading of oscillating value shown in the display.

Procedure to Calculate the Air changes

  Calculate the supply grill area A= Length (in ft) x Width (in ft).

Calculate the supply grill Average velocity V= (V1+V2+V3+V4+V5 ) /5.( in ft/min) .

Calculate the air flow delivered by each supply grill in CFM   = A x V (in CFM).

Find the total quantity of supply air delivered in to the room in CFM by adding all             supply grills air flow CFM.

Calculate the air changes by below given formula.

                    Air changes per hour = Total supply air flow rate (CFM) in the clean room x 60

                                                                        Volume of the clean room (cu. ft)          

Example :

Air velocity =  100 feet per min

Air Flow =  Velocity Ft/ min x grill area(Ft²⁾

                              =  100 x 4 =400 Cubic feet per min(CFM)

If room has two supply grills, sum the two air flows = 400+ 400= 800 CFM

Air changes = Air flow x 60

Room volume(Ft³ )

=800 Ft³x 60 min

  1000 Ft³

= 48 Air changes per hour (Limit : Not less than 25 air changes per hour for ISO 8)

There are 5 tests during AHU Qualification.

S.NO	Test	Frequency	Instruments used	Acceptance criteria
1	Air Changes	For every six months (on or before 7 days)	Anemometer for Velocity of air	Not less than 25 air changes per hour
2	Particle count “At Rest Condition”		Particle counter	Not more than 3520000 for ISO 8 There is an equation to estimate particle limit.
3	HEPA Filter Integrity Test (Leak Test)		Aerosol Photometer and Aerosol generator using compressed air	No leak should be observed Not more than 0.01% leak
4	Recovery test	For every one year (on or before 15 days)	Particle counter	Recovered within 15 minutes, after polluting the room with aerosols
5	Air flow pattern		Dry ice in hot water to generate SMOKE	Uni-directional and positive and negative pressure should be indicative.

Regards,
Bujji Reddy.
9676749937