. 2016 Feb 9;33(3):193–210. doi: 10.1177/0748233715619072

Table 3.

Non-task benzene air concentrations by job title, operational status, and area.

Job title (percent of total)^a	Description of duties	Status	Area(s)	n	Detection frequency (%)	Benzene concentration (ppm)
Job title (percent of total)^a	Description of duties	Status	Area(s)	n	Detection frequency (%)	Mean	Standard deviation	Geometric mean	Geometric standard deviation	75th percentile	95th percentile	Minimum detected	Maximum detected
Process technician (48%)	Process operations, such as draining process equipment or lines prior to work and taking samples of process streams	Routine	Lube blending and storage	135	6%	0.015	0.041	ND	ND	ND	0.055	0.034	0.39
			Hydrofiner	299	44%	1.1	7.0	ND	ND	0.18	1.0	0.010	91
			Hydrocracker	138	62%	0.074	0.11	0.023	7.5	0.093	0.26	0.010	0.95
			Reformer	908	47%	0.084	0.15	ND	ND	0.11	0.24	0.0090	2.0
			Waste treatment	697	58%	0.13	0.19	0.037	7.1	0.20	0.45	0.0080	1.6
			Tank farm	224	54%	0.090	0.30	0.014	7.0	0.060	0.34	0.010	3.6
			Pipestills	357	43%	0.074	0.33	ND	ND	0.040	0.19	0.010	5.1
			Analyzer	18	100%	0.12	0.19	0.069	2.8	0.090	0.44	0.010	0.80
			All other areas	2540	29%	0.068	1.0	ND	ND	0.028	0.16	0.006	49
		Startup	All areas	57	39%	0.041	0.062	ND	ND	0.040	0.16	0.015	0.29
		Turnaround	Hydrocracker	39	95%	0.17	0.28	0.077	3.3	0.12	0.93	0.030	1.3
			Reformer	133	77%	0.28	0.88	0.055	7.2	0.21	1.19	0.0070	9.2
			All other areas	381	43%	0.049	0.093	ND	ND	0.048	0.24	0.010	0.52
Machinist (12%)	Equipment maintenance/repair on refinery units	Routine	Waste treatment	309	74%	0.34	0.74	0.087	7.7	0.34	0.91	0.010	6.2
			reformer	68	57%	0.51	1.6	0.045	12	0.19	2.1	0.040	11
			All other areas	958	31%	0.074	0.39	ND	ND	0.038	0.26	0.0050	7.7
		Turnaround	Lube extraction unit	49	33%	0.021	0.025	ND	ND	0.035	0.06	0.024	0.06
			Reformer	39	90%	0.28	1.1	0.082	3.4	0.12	0.32	0.030	7.0
			All other areas	97	52%	0.065	0.11	0.020	6.5	0.060	0.29	0.020	0.76
Pipefitter/welder (10%)	Piping maintenance, including blinding and breaking of lines	Routine	Reformer	77	74%	0.69	1.8	0.093	8.1	0.49	3.1	0.010	12
			Waste treatment	71	69%	0.12	0.19	0.034	6.7	0.13	0.53	0.0050	0.92
			All other areas	777	37%	0.12	0.88	ND	ND	0.036	0.31	0.0010	16
		Turnaround	Reformer	135	75%	0.44	1.6	0.061	8.4	0.20	1.9	0.013	15
			Lube extraction unit	46	26%	0.029	0.061	ND	ND	0.023	0.13	0.013	0.32
			All other areas	168	61%	0.11	0.27	0.026	6.2	0.11	0.41	0.010	1.9
Laboratory technician (10%)	Analysis of samples of process streams and other laboratory work	Routine	All areas	1187	58%	0.17	0.71	0.024	8.1	0.11	0.60	0.0035	14
		All	All areas	12344	43%	0.21	2.4	ND	ND	0.070	0.44	0.0010	140
		Routine	All areas	10754	42%	0.21	2.3	ND	ND	0.070	0.42	0.0010	140
		Startup	All areas	57	39%	0.041	0.062	ND	ND	0.040	0.16	0.015	0.29
	All Job Titles^b	Turnaround	All areas	1533	49%	0.25	3.1	ND	ND	0.080	0.53	0.0040	103
		1976–1989	All areas	7259	53%	0.27	2.6	ND	ND	0.12	0.55	0.0050	140
		1990–2007	All areas	5066	29%	0.14	2.0	ND	ND	0.026	0.21	0.0010	103

^aTotal percentage for job titles shown is 80%.

^bTotal includes all job titles; Year of sample collection, unknown for 19 samples. ND: Geometric mean and geometric standard deviation not calculated because more than 50% of the samples were below the limit of detection. Percentile not calculated because the proportion of results below the detection limit exceeds the selected percentile.