Table 1.

Federal Standard 209E. Class limits are given for each class name.

Class name		Class limits
		≥0.1 µm		≥0.2 µm		≥0.3 µm		≥0.5 µm		≥5 µm
SI	English	m3	ft3	m3	ft3	m3	ft3	m3	ft3	m3	ft3
M1		350	9.91	75.7	2.14	30.9	0.875	10.0	0.283
M1.5	1	1,240	35	265	7.50	106	3.00	35.3	1.00
M2		3,500	99.1	757	21.4	309	8.75	100	2.83
M2.5	10	12,400	350	2,650	75.0	1,060	30.0	353	10.0
M3		35,000	991	7,570	214	3,090	87.5	1,000	28.3
M3.5	100			26,500	750	10,600	300	3,530	100
M4				75,700	2,140	30,900	875	10,000	283
M4.5	1,000							35,300	1,000	247	7.00
M5								100,000	2,830	618	17.5
M5.5	10,000							353,000	10,000	2,470	70.0
M6								1,000,000	28,300	6,180	175
M6.5	100,000							3,350,000	100,000	24,700	700
M7								10,000,000	283,000	61,800	1,750