1.0 OBJECTIVE
To lay down the procedure for carrying out airborne particle count in the static condition.2.0 SCOPE
This SOP shall be applicable for clean rooms, corridors, laminar air flow and process equipment.3.0 RESPONSIBILITY
Officer /Executive/ Assistant Manager4.0 ACCOUNTABILITY
HOD engineering5.0 PROCEDURE
5.1 Ensure that the area is cleaned and air handling unit is kept ON for at least two hours before taking particle count.5.2 The particle count to be performed by an outside agency.
5.3 Ensure that the particle counter used is duly calibrated and the certificate for the same must be traceable to national/ international standards.
5.4 Sample 1 cubic feet of air per minute under normalized mode.
5.5 Calculation for the number of locations for particle count
5.5.1 Number of sample locations shall be taken as the square root of the area in meter square of clean room/zone.
5.5.2 This number shall be rounded up to a nearest higher number.
5.5.3 If the number of location is one then minimum three samples shall be taken at that location.
5.6 The locations for taking the samples shall be near doors, return air raisers, at corners and near equipment.
5.7 The count shall be always taken for 1 minute and at working height of about 1 meters from the ground level.
5.8 After completion of the particle count in a particular room/ zone take the printout.
5.9.1 The particle count for particle size 0.5 are printed in cubic feet. The printout shows the sampled quantity of air as 1.000 cfm.
5.9.2 Convert particle count obtained in cubic feet to the particle in cubic meter by multiplying with factor 35.31.
5.10 Calculate for mean, standard deviation and 95% upper confidence limit, as follows
5.10.1 Computation of average particle concentration at a location (P)
( T1 + T2 + ……… + TX )
P = -----------------------------------
X
Where,P: Average particle concentration at one location
T1 to TX: Particle concentration of individual samples
X: Number of samples taken at the location
5.10.2 Computation of mean of the averages ( M )
( P1 + P2 + ……… + PY )
M = ----------------------------------
Y
Where,M: Mean of averages
P1 to PY: individual location averages
Y: Number of individual location averages
5.10.3 Computation of standard deviation of the mean ( SD )
(P1 – M) 2 + (P2 – M) 2 + …….. + (PY – M )2
SD = √ ----------------------------------------------------
( Y – 1 )
Where,
SD : Standard deviation of the mean
5.10.4 Computation of 95% upper confidence limit ( UCL )
SD
95% UCL = M + ( t X ------)
√Y
Where t factor for 95% upper confidence limit is as given in table
Number of individual averages ( Y )
|
2
|
3
|
4
|
5
|
6
|
7- 9
|
t
|
6.3
|
2.9
|
2.4
|
2.1
|
2.0
|
1.9
|
5.12 When only a single location is sampled or when more than nine are sampled computing the mean, standard deviation and 95 % upper confidence limit is not applicable.
5.13 The frequency for taking the particle count
5.13.1 For clean rooms, corridors and process equipment shall be once in six months.
5.13.2 For laminar air flow shall be once in six months.
5.13.3 The particle count testing shall be carried out as per schedule.
5.14 Acceptance Criteria
5.15.1 The cumulative particle concentration for the area should not exceed the desired class limit as given below
Specified By
|
Class
|
0.5μ
|
5.0μ
|
||
Cubic meter
|
Cubic feet
|
Cubic meter
|
Cubic feet
|
||
ISO 14644
|
Class - 5
|
3,520
|
100
|
29
|
0
|
Class - 7
|
3,52,000
|
10,000
|
2,930
|
70
|
|
Class - 8
|
35,20,000
|
1,00,000
|
29,300
|
700
|
|
In - house
|
100
|
3,500
|
100
|
0
|
0
|
10,000
|
3,50,000
|
10,000
|
2,000
|
57.14
|
|
1,00,000
|
35,00,000
|
1,00,000
|
20,000
|
571.43
|
|
5.15 Process equipment having air handling unit shall meet the Class 10,000 requirements.
5.16 The particle count should meet the In-house specified limits.
6.0 ABBREVIATION
6.1 SOP: Standard Operating ProcedureAlso see: HVAC System Validation Tests
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