What works excellent:
We have a new trailer and for the past two summers it has been left in Key largo, (think high humidity) for six months.
We asked all our neighbors who have been here for many years what they do.
It is just the opposite of what everyone else is telling you.( no damp rid and no ventilation)
The office at our RV park as well as the local RV dealer here in Key Largo carry it.
It is little packs that you open and put on the Floor (the directions tell how many per square feet, and I think we use three for a 37 foot trailer.)
The Directions: The RV should be closed as tight as possible, (have no ventilation- Close all vents and openings).
When you open the RV back up dispose of the little packs and open all the windows and doors to air it out and while it is airing out don't go in it.
The directions also state that it will not work if vents are open or if air is being circulated
The first year we used it we were amazed at how perfect it worked The trailer looked brand new, when we opened it up and then again the same this year, (zero mold and not a dead or live bug to be found).
Needless to say we will be using it again when we head north in the spring
We used the one from the RV dealer which is a little different then the one the RV park carries, and if you want the name of it I can call them and get it for you.
Jack L