PARTICLE COUNT TESTS(AT REST)

PARTICLE COUNT TESTS(AT REST)

Objective:

This test is undertaken to verify that the system can provide the required airborne particulate cleanliness classification as defined in the design specification in the “at rest” condition.

Acceptance Criteria:

The particle counts should not exceed the airborne particulate cleanliness classification identified within EN ISO 14644, clean rooms & Associated Controlled Environments, part 1, Classification of Air Cleanliness.(Class 8).

Class limits in particles of size equal to, or greater than, 0.5µm and 5.0µm are shown below:-

Classification ISO 14644	Allowable number of “At Rest” particles per cubic meter at 0.5 µm	Allowable number of “At Rest” particles per cubic meter at 5.0 µm
ISO Class 8 (At Rest)	3,520,000	29,300

Test Equipment:

Calibrated light scattering particle counter.

These tests can only be carried out after a complete clean of facility has occurred.

The test methodology, including the calculation of sample locations and volumes, is based upon ISO 14644:1999 Clean rooms & Associated Controlled Environments, Part 1, Classification of Air Cleanliness.

Calculating the Number of Sample Locations:

The number of test locations should be calculated using the formula given below. The number of locations may be seen in the table provided whilst the count locations within each room should be shown on a drawing as an appendix-2.

   Number of locations NL=√A(Square Root of A, Where

NL=Minimum number of sampling locations(rounded up to a whole number)

A=Area of the clean room or Clean zone is square meters.

The number of location shall be rounded off to the nearest whole number.

Ensure that the sampling locations are evenly distributed throughout the area of clean room and positioned at the height of the work activity.

Calculating the Sample Volume:

The minimum sample volume per location is 2 litres.

The minimum sample time at each location must be one minute or greater.

There  is no definition of the number of samples to be taken at each sample point except in the case when there is only one sample point. For one sample point, there must be at least three sample volumes taken.

If the number of sample locations is at leas two but not more than nine, then the Upper Confidence Limit(UCL) will also be calculated, and the calculated value for the UCL must also be less than the classification limit.

If the number of sample locations is greater than 10 and more than one sample was collected per location, then the classification is determined by the averages of the particle counts obtained at each location. The calculated average at each location must pass the classification limit.

If the particle counter is set-up to operate at a flow rate of 1ft³ per minute, then the particle count value will need to be multiplied by 35.31 to convert particles per ft³ to particles per m³.

Performing the Practical Work:

The methodology should be undertaken in accordance with EN ISO 14644:1999, Part 1.

Configure the particle counter to calculate the 95% Upper Confidence Limit value derived from the particle counts, for particle sizes of 0.5µm and 5.0µm.

Record the 95% UCL values within the result table, identifying any non-conformances.

Append all raw data and calculation sheets.(The print out of the particle count shall ne checked and the same shall be duly signed and filed along with a photocopy).

Number of test positions and samples:

Room No	Room Description	Floor Area(m²)	No. fo Test positions	No. of Test Samples per location

Duration:

Carry out the airborne particle count for three consecutive days.

Acceptance criteria:

Particles count.	(At rest(Per m³)		In Operation(Per m³)
	≥0.5µ	≥5µ	≥0.5µ	≥5µ
Class C	352,000	2900	35,20,000	29000
Class D	35,20,000	29000	Not defined	Not defined

The clean room or clean zone is deemed to have met the specified sir cleanliness classification if the averages of the particle concentrations measured at each of the locations and, when applicable, the 95% upper confidence limit, do not exceed the concentration limits(for 0.5 and 5.0 micron) given in the above said Table.

AREA CLEANLINESS CLASSIFICATION

Sr. No	Std EC Grade			Particles/M³
				≥5µ		≤0.5 µ
1.	Grade A	At Rest		20		3,520
		In Operation		20		3,520
2.	Grade B	At Rest		29		3,520
		In Operation		2,900		3,52,000
3.	Grade C	At Rest		2,900		3,52,000
		In Operation		29,000		3,520,000
4.	Grade D	At Rest		29,000		3,520,000
		In Operation		Not defined
Sr. No	WHO			Particles/M³
				≥5µ		≤0.5 µ
5.	Grade A	At Rest		0		3,500
		In Operation		0		3,500
6.	Grade B	At Rest		0		3,500
		In Operation		2,000		3,50,000
7.	Grade C	At Rest		2,000		3,50,000
		In Operation		20,000		35,00,000
8.	Grade D	At Rest		20,000		35,00,000
		In Operation		Not defined		Not defined

ISO Classification Number	Particles/M³
	≥5µ	≤0.5 µ
ISO Class 5	29	3,520
ISO Class 7	2,930	3,52,000
ISO Class 8	29,300	3,520,000
ISO Class 9	2,93,000	35,200,000