Tank and barge cleaners do some of the dirtiest, little-known work in industry.

Chemicals and petroleum travel in tanker trucks, rail tank cars and inland barges.

When sludge builds up inside, or when someone wants to ship a different material in the container, they send it to be cleaned.  There are machines, like wash heads that help with the task, and sometimes do it all.

But, sometimes a person has to go inside to scrape off stubborn remainder or blow the container dry.

Those remainders –- sometimes hundreds of gallons — can give off lethal or sickening gases.

OSHA rules require many protections -– air testing, breathing masks, Tyvek suits, lifelines to pull a man out.

But, the Houston Chronicle found two out of every three facilities has not had a health and safety inspection by OSHA in more than 10 years. Those facilities that were inspected had an average of nine violations.

The red diamonds on the map below show places that clean containers where no record of OSHA visits was found. The purple diamonds are where OSHA has been on site at least once in the last decade. You can zoom way in, and click on an individual site to see its records or website. To hear what the work is really like, and read the story of one father who cleaned rail cars, visit www.houstonchronicle.com.