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)
Naphthalene C10H8	60	Phenol	0.5-14	2	2*	T		-
Nickel carbonyl Ni(CO)4	20L	Nickel carbonyl	200-800	1	3	-		0.05
			10-200	4
Nitric acid HNO3	15L	Nitric acid	20-40	1/2	3	H		2
			1-20	1
			0.1-1	2-10
	80	Acid gases	5-100	2	2	-
Nitroethane CH3CH2NO2	52	Nitroparaffin (Pyrotectube)	4-240	1	3	-		100
Nitrogen dioxide NO2	9L	Nitrogen dioxide	30-125	1	3	-		3
			0.5-30	2
	10	NO+NO2	2.5-200	1	3	+
	80	Acidgases	0.2-4	2	2	-
Nitric oxide NO	10	NO+NO2	5-200	1	3	+T		25
			2.5-5	2
Nitrogen oxides NO+NO2	11HA	Nitrogen oxides	50-2500	1	2	-		-
	11S	Nitrogen oxides	250-625	1/2	2	-
			10-250	1
			5-10	2
	11L	Nitrogen oxides	5-16.5	1	3	-
			0.2-5	2
			0.08-0.2	4
			0.04-0.08	8
Nitromethane CH3NO2	52	Nitroparaffin (Pyrotectube)	5-300	1	3	-		20
1-Nitropropane CH3CH2CH2NO2	52	Nitroparaffin (Pyrotectube)	4.2-252	1	3	-		25
2-Nitropropane (CH3)2CHNO2	52	Nitroparaffin (Pyrotectube)	3.7-222	1	3	-		10
Nitrotrichloromethane	See Chloropicrin
Nonane CH3(CH2)7CH3	105	Hydrocarbons(HigherClass)	260-3900	1	3	-		200
			130-260	2

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