We keep a pack of "Always" or "Depends" type absorbent sheets on hand at the house to corral unexpected water leaks, etc. (hot water heaters, dish washers, sink fixtures, what-ever).
Well, they are also really good at absorbing diesel fuel leaks/spills in tight areas. So much so that I may consider having a pack on the rig when traveling.
A while back I was working on the Aqua Hot system and had a small fuel leak develop due to the end of the fuel line cracking. Our unit is located on the interior of the center bay, and it's tight quarters.
I clamped off the fuel line, but couldn't easily get a container in there to drain the residual in the line without making a real mess. The absorbent sheets worked great at absorbing and containing the residual fuel. I was able to lay one out below the fuel line so that when it was unclamped the pad captured the fuel.
They are also thin enough to fold and slide into tight areas so soak up fuel that had gotten onto the pan in hard to reach areas. It makes final clean up of the pan much easier with a degreaser type product.
The used pads were sealed up and taken to the local county hazmat facility and accepted without question.
Chris