Gas or Vapour to be Measured Chemical Formula	Réf tube	Gastec Tube No. & Name	Measuring Range (ppm)	No.of Pump Strokes	Shelf Life (year)	Note		TLV- TWA,C (ACGIH) (ppm)
Benzaldehyde C6H5CHO	91L	Formaldehyde	4-92	1	3*	T		-
Benzene C6H6	121	Benzene	60-120	1	3	-		0.5
			5-60	2
			2.5-5	4
	121L	Benzene	12-60	1	3	+
			0.25-12	5
			0.125-0.25	10
	121S	Benzene	120-312	1	3	+
			5-120	2
			2-5	4
	121SL	Benzene	20-100	1	3	+
			1-20	5
	121SP	Benzene	0.5-10	3	2	+
	171	Acetylene	0.03-0.6%	4	3	T
Benzyl bromide C6H5CH2Br	136L	Methyl bromide	25-850	1	2	+		-
Benzyl chloride C6H5CH2Cl	132L	Trichloroethylene	0.8-20	2	2*	T		1
Boron trichloride BCl3	12L	Hydrogen cyanide	0.5-20	2	2	H		-
Bromine Br2	8La	Chlorine	0.05-0.8	4	3	-		0.1
Bromochloromethane	See Chlorobromomethane
Bromoform CH3(CH2)2CH3	136L	Methyl bromide	1-50	1	2	+		0.5
			0.5-18	2
1,3-Butadiene CH2:CHCH:CH2	174	1,3-Butadiene	50-800	1	3	T		2
	174L	1,3-Butadiene	5-100	4	3	T
			2.5-5	8
	174LL	1,3-Butadiene	0.5-5	1	3*	-
Butane CH3(CH2)2CH3	104	Butane	25-1400	1	3	-		800
	103	Hydrocarbons (Lower Class)	0.84-1.68%	1/2	2*	++
			0.07-0.84%	1
			0.035-0.07%	2
n-Butanol CH3CH2CH2CH2OH	114	n-Butanol	10-150	3	3	T		C 50
sec-Butanol CH3CH2CH(OH)CH3	115	sec-Butanol	5-150	3	3	T		100
2-Butanone	See Methyl ethyl ketone(MEK)
Butyl acetate CH3CO2(CH2)3CH3	142	Butyl acetate	0.05-0.8%	2	3	T		150
	142L	Butyl acetate	10-300	2	2	T		-
tert-Butanol (CH3)3COH	102L	n-Hexane	0.05-1.2%	2	3	-		100
Butylamine CH3(CH2)3NH2	180	Amines	5-100	1	3	T		C 5
	180L	Amines	0.4-8	1	2	T
Butyl mercaptan CH3(CH2)3SH	70L	Mercaptans	6.4-12.8	1/2	2	-		0.5
			0.8-6.4	1
			0.32-0.8	2
			0.16-0.8	4
tert-Butyl mercaptan (CH3)3CSH	75	tert-Butyl mercaptan	60-150mg/m3	1/2	2	T		-
			30-60mg/m3	1
			2.5-30mg/m3	2
	75L	tert-Butyl mercaptan	15-30mg/m3	1/2	2*	T
			1-15mg/m3	1
			0.5-1mg/m3	2
	77	TBM&DMS	1-15mg/l	1	2*	+T
	70L	Mercaptans	4-8	1/2	2	-
			0.5-4	1
			0.2-0.5	2
			0.1-0.5	4
Butyric acid CH3CH2CH2CO2H	81L	Acetic acid	0.325-13	1	2*	T		-
Butyronitrile CH3CH2CH2CN	191L	Acrylonitrile	15-360	1	3	+		-

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T:Temp Correction H:Humidity Correction +:Twin Tubes ++:Nine Tubes *:Refrigerator Store

Mesh:Correction Factor/Chart