Every year, when the first heavy rains arrive, dengue case numbers in Thailand climb sharply. Local authorities are the first line of defence, and the residents' first phone call. Their arsenal is small, and one of the most important weapons in it is the thermal fogging machine sitting in the equipment store.

The problem is that this weapon is usually forgotten until the day it is genuinely needed, and that day is almost never a day that can wait. By then a child in the neighbourhood is already in hospital, an order has already come down from management, and residents are already standing at the mouth of the soi.

This article tells the true story of a mid-sized municipality in central Thailand whose fogger would not start on the most important morning of the season. It also explains what really causes this fault, why do-it-yourself fixes usually make the machine worse, and what the correct solution looks like.