Why did they not make some sort of remote firing fixture?
From the time the facility was built and up until the 1980's, I don't think the safety bug had bitten the company. Most of the employees were the typical small-town and rural men who were a tad casual about safety anyway.
(It was quite common for farmers and men at elevators and crop production businesses to be missing fingers, etc... sort of like railroaders a generation earlier.)
My guess is that cleaning the stacks wasn't done that often, was seen as just another part of the job.