No. A FumoFlow grain shed is not a fully sealed shed in the same way as a gas-tight silo or a purpose-sealed bulk grain storage shed. Instead, the tarp is sealed to the shed structure, so the fumigation zone is the sealed space under the tarp, not the whole shed envelope. For fumigation purposes, it is the area under the tarp that must hold gas at the required concentration for the required time.

This approach has some important advantages:

1. Less fumigant is required
   Fumigant dose is based on the volume of the enclosure being treated. Because a FumoFlow system only seals the space under the tarp, rather than the full shed airspace, the treated volume is smaller, so the total fumigant required is lower than it would be for a fully sealed shed of the same footprint.
2. Less pressure-driven gas loss from thermal movement
   In rigid silos and sheds, normal ambient temperature changes create pressure changes inside the storage. These pressure changes can force air to exchange through any leaks and greatly accelerates fumigant loss. A FumoFlow tarped enclosure is more flexible than a rigid sealed vessel, so it is less prone to those same expansion and contraction pressure effects pushing gas out or pulling fresh air in. This helps the fumigation environment remain more stable.