Vessel Fumigations

September 2025 Edition:

Vessel Fumigations by: Lance Grey

Vessel Fumigation with Recirculation: Enhancing Efficiency and Safety

Vessel fumigation is a crucial procedure in global maritime trade, particularly for bulk cargoes such as grains, pulses, and other agricultural commodities that are prone to insect infestation. Among various fumigation techniques, fumigation with recirculation has emerged as a preferred method due to its enhanced gas distribution, reduced treatment times, and improved safety profile.

What is Fumigation with Recirculation?

Fumigation with recirculation is a process in which the fumigant gas, once introduced into the fumigation space (typically cargo holds), is actively circulated using a system of fans and ducts. Unlike passive fumigation-where the gas disperses slowly and unevenly-recirculation systems force the movement of gas, promoting uniform distribution throughout the cargo.

Why Use Recirculation?

Traditional fumigation can suffer from uneven gas concentrations, especially in deep cargo holds, dense commodities, or when gas pathways are obstructed. Recirculation addresses these issues and offers several advantages:

Benefits of Recirculation Fumigation

Faster gas dispersion and penetration into cargo

More uniform concentration levels throughout the treatment area

Improved efficacy against target pests, including burrowing insects

Shorter exposure times due to enhanced distribution

Reduced fumigant quantities may be needed for the same effect

Lower risk of underdosing or overdosing in parts of the hold

Better compliance with quarantine or export requirements

A typical recirculation system includes

Gas introduction points (usually at the top or middle of the hold)

Flexible ducting or piping

Electric or pneumatic fans/blowers

Return ducts (drawing gas from the bottom of the hold)

Monitor ports for sampling gas concentration at multiple depths