Information is subject to change at any time.
Always check the label of the product to insure that you use it correctly.
There are other brand names and formulations of the products listed below. These are only the most common forms. If you wish to use a similar product, check the label to insure it is registered for the intended use.

Applied to boots of elevators, beneath false floors etc This is an "empty" space fumigation targeted at the space beneath the perforated floor in a metal grain bin. See the WARNING below.

Recommendations

Chloropicrin
1 to 2 qt empty / bin (smaller bins)
3 to 4 qt empty / bin (greater than 50,000 bu)

Chloropicrin is significantly heavier than air and is therefore preferred for "clean-out" fumigations. However, though it is still labeled for "clean-out" of empty bins, it may not be available due to shipping constraints. Chloropicrin is highly corrosive to most metals. DO NOT USE CHLOROPICRIN TO TREAT GRAIN!
NOTE: Applied by volume not bushels

Methyl bromide
1 to 3 Ibs. per 1000 cubic feet.

Methyl bromide is significantly heavier than air and is therefore appropriate for fumigation under perforated floors in grain bins. However, it is quite corrosive to many materials. Check the label before using. DO NOT USE METHYL BROMIDE TO TREAT GRAIN!
NOTE: Applied by volume not bushels

Aluminum phosphide
tablets 20-60 /1000 cubic feet
pellets 100-300 /1000 cubic feet

Aluminum phosphide is not significantly heavier than air and is therefore not the preferred product. However, it is labeled for this use and is easily available. Because of it's light and penetrating nature very close attention must be paid to sealing the area to be treated.
NOTE: Applied by volume not bushels