Large municipalities favour vehicle-mounted ULV cold foggers because they cover wide areas quickly, which suits main roads and wide lanes treated in the pre-dawn hours.

But this class of machine operates under conditions entirely unlike a backpack unit. It runs longer, absorbs vibration continuously, and usually draws power from the vehicle's electrical system. Those three factors create failure modes of their own.

This article follows a city municipality in eastern Thailand whose truck-mounted fogger died mid-route on an important morning, and explains the most common causes and how to stop them recurring.