1.0 OBJECTIVE:
To lay down procedure for carrying out air
borne particle count in 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 Manager
4.0 ACCOUNTABILITY:
HOD engineering
5.0 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 air per minute under normalized mode.
5.5 Calculation for number of locations for particle count
5.5.1 Number of sample locations shall be taken as square root of
the area in meter square of clean room/zone.
5.5.2 This number shall be rounded up to 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. mand 5.0 m. The printout shows sampled quantity of air as 1.000
cfm.
5.9.2 Convert particle count obtained in cubic feet to 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

5.11 If the 95% UCL value exceeds the class limit , take the count
at additional evenly distributed locations and compute the 95% UCL for all
locations which should not exceed the desired class limit.
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 equipments 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

5.15.2 The 95% UCL of particle concentration for the area should
not exceed the desired class limit.
5.15 Process equipment having air handling unit shall meet the
Class 10,000 requirements.
5.16 The particle count should meet the Inhouse specified limits.
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