Normally you keep floating roof tanks errr floating.

Fill the tank with something that doesn't"smell"?

But as this should be a rare event then maybe you just need to deal with it once every few years.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

Check the foam seals and weather shrouds. There could be gaps in between the shell and the foam seal at some locations.

DHURJATI SEN

During your initial fill, the vapor space under the floating roof has to go somewhere. So, it comes out and of course it smells. You can reduce the odors by filling smoothly and for the least amount of time (both to reduce the concentration of product in the space). You can nearly eliminate the emissions (and odors) if you collect these vapors and either destroy them or condense them and put the resulting liquid back into the tank. Collection happens by creating a small vacuum under the floating roof with a blower and a vapor pole (or sometimes a small shell nozzle). Destruction happens using a thermal oxidizer (perhaps one at your dock) or portable device (normally an internal combustion engine running on make-up gas with exhaust monitoring). Vapor recovery would be a carbon bed type device or other type of condenser (perhaps used at your truck rack). These are all fairly common solutions that function well under ideal conditions.

Thank you all very much!