Measuring ethylene contamination in storage areas remains a difficult task because the active levels of ethylene are so low (50 parts of ethylene in a billion parts of air, or even less).

In most studies, and for most flowers, we find that dry storage is superior to wet storage.  If you are storing the gerberas in a cool room, it is vital that the temperature be low enough.&nbs

Unfortunately there are no publicly available references for vacuum cooler design.

The general rule for refrigerated storage is to use 100 cfm per ton of product until the product reaches storage temperature and after that the air volume can be reduced to 20 to 40 cfm per ton.&nb

You are correct, the recommended long term storage conditions for onions are 0°C and 65 to 70% relative humidity.

Good quality humidity sensors cost at least $500.

Grape storages in California almost exclusively use the method you describe.  Grapes are first forced-air cooled in a separate cooling room.

Specific heat of foods is used to calculate the heat that must be removed during initial cooling.

Our web site has a publication on small scale cold rooms and it has a plan for a farm-built cold room.  See <http://ucce.ucdavis.edu/files/datastore/234-701.pdf.