Using Semiconductor Heater in Dusty, Damp, or Demanding Settings

https://precision-heating.iamarrows.com/beginner-s-guide-to-pi-heater-what-to-know-before-you-specify-one

Many heating problems look like a power problem at first. In practice, the cause may be contact, heat loss, sensor position, or poor fit. A semiconductor heater works best when these parts are planned together