Great topic!
Brian hit the nail on the head so that means he's been paying attention which is always a good thing. :thumbsup:
And Frank The Tank is right about the danger of the vapors.
I've done some checking online and found this CDC related web site which addresses filling the cans:
http://www.cdc.gov/niosh/hid2.html
Here's some text from that webpage:
In recent incidents reported to the National Institute for Occupational Safety and Health (NIOSH), fires spontaneously ignited when workers or others attempted to fill portable gasoline containers (gas cans) in the backs of pickup trucks equipped with plastic bed liners or in cars with carpeted surfaces. Serious skin burns and other injuries resulted. Similar incidents in the last few years have resulted in warning bulletins from several private and government organizations.
These fires result from the buildup of static electricity. The insulating effect of the bed liner or carpet prevents the static charge generated by gasoline flowing into the container or other sources from grounding. The discharge of this buildup to the grounded gasoline dispenser nozzle may cause a spark and ignite the gasoline. Both ungrounded metal (most hazardous) and plastic gas containers have been involved in these incidents.
Prevention:
Construction workers and others in small businesses who often work with gasoline-powered equipment commonly use portable gasoline containers. Homeowners use gasoline cans for their lawnmowers and other equipment.
Avoid the hazardous practice of leaving the portable gasoline containers in pickup trucks or cars when refueling!
Before filling, always remove the containers from the vehicle and place them on the ground at a safe distance from the vehicle (provides path to dissipate static charge to ground).
Touch the container with the gas dispenser nozzle before removing the container lid (provides another path to dissipate static charge to ground).
Keep the nozzle in contact with the container inlet when filling (to dissipate static charge buildup from flow of gasoline).
Additional measures for prevention include the following:
Manufacturers or retailers: Place a hazard label on all plastic liners being sold warning workers not to fill portable gas containers in the bed liner of the truck but always to place the containers on the ground before filling.
Gas stations: Display a warning notice near gas pumps to place all portable gas containers on the ground before filling.
States: Provide a warning notification to owners and users when new vehicles are licensed or when license plates are renewed.
Manufacturers: Build bed liners that can be grounded to the metal truck bed, thereby dissipating potential electrostatic charge.
The concern now is carrying the containers in the truck and any discharge of static electricity around the container (such as when sliding the container prior to lifting it out of the bed).
Note that the webpage says, "the insulating effect of the bed liner or carpet prevents the static charge generated by gasoline flowing into the container or other sources from grounding."
I wonder if any static charge built up by our bodies could discharge to the containers when we handle them although I suspect it won't because the container is insulated.
Certainly it's a good idea to first ground oneself to the truck body before touching the gas cans.
I called CDC (!!!) about this and the contact on the phone had to research it. They weren't able to find any information in regard to that concern and they directed me to the US Consumer Safety Commission hotline and they suggested I contact the container manufacturer. I think a call to a gas company hotline would probably be the next step (Shell, Exxon/Texaco, etc.)