Second, it's potentially dangerous to users. Here's what he writes in his newsletter, From the UC Apiaries . It boils at 216 degrees F, melts at 35 degrees F, has a specific gravity of 1.2, a vapor pressure of 23 mm Hg at 20 degrees C, mixes well with water, alcohol, ether and glycerol, and has an odor threshold at 21 ppm. The vapors are heavier than air and may travel a considerable distance to source of ignition and flashback. However, fire is not a major concern.
Organic acids are dangerous materials to handle.
If you spill formic acid on your skin, expect severe pain, brown or yellowish stains, burns that usually penetrate the full thickness of the skin, have sharply defined edges, and heal slowly with scar tissue formation. The most subtle effects involve inhalation. Opening a container of formic acid in an enclosed space liberates fumes. At 100 ppm, the fumes are immediately dangerous to life and health. Breathing only a little at a time over prolonged periods can lead to erosion of the teeth, local tissue death in the jaw, bronchial irritation with chronic cough, frequent attacks of bronchial pneumonia and gastrointestinal disturbances.