SPRINGFIELD, Ill. (WAND) - Staff call them the "ghosts" of the Abraham Lincoln Presidential Library and Museum (ALPLM). The engineers at ALPLM work behind the scenes, keeping artifacts at the museum and library safe.

They are not protecting them from thieves or vandals, but instead from heat and humidity. With artifacts older than the Civil War, they must be kept in very specific conditions. "These aren't just pieces of paper, this is really historic documents and information," said Dorothy Hutchinson-Gross, Director of Facilities and Sustainability at ALPLM. "T he swings in temperature and humidity can really be a problem versus having something that's maintained in constant throughout the life of that document."

The team of engineers uses a complex tracking system to see the exact

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