Benzaldehyde, which smells like almonds, is a  liquid which can be used
to clear bees from supers.
   Recently, I have seen and heard warnings about the spontaneous combustion
of benzaldehyde and of the crystals which form on the fume board (benzoic
acid?).  These warnings were cautions about storing fume boards between
uses.
   A search of the internet brings up websites that match benzaldehyde or
benzoic acid with spontaneous combustion, but, while the text of the sites
discusses storage dangers of various chemicals, it shows no link between
these two chemicals and spontaneous combustion.
  Are stored benzaldehyde or benzoic acid fire hazards?
  Does washing a fume board with water remove the chemicals? (Are they water
soluble?)
Tim
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Tim Sterrett
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(southeastern) Pennsylvania, USA
40.0 N 75.5 W