I urge you to check out this strong story about acute deaths among young oil field workers working alone to measure oil levels in rural tank farms. It has some strong and insightful words from Association of Occupational & Environmental Clinics (AOEC) President and UCSF Professor Bob Harrison.
Also see Dr. Harrison and colleagues very useful report in the MMWR on this same topic from January, 2016: http://www.cdc.gov/mmwr/volumes/65/wr/mm6501a2.htm.