FBI building evacuated for anthrax scare today. There is a 2004 Homeland Security/FBI document relating to the risk of attack on an HVAC system. Basically, it provides the advice of closing the intake if the aerosol is coming from outside and opening it if the aerosol is coming from inside. But perhaps the latter advice is misconceived — as that would risk spreading it to adjacent buildings. It seems evacuation is what you should do.
#1. The silica on the Dugway spores is the result of static electricity, NOT van der Waals forces.
#2. The idea of gluing silica particles to spores as "spacers" is STUPID beyond belief.
#3. The silica wasn't deliberately glued to the Dugway spores, it was a bad side effect of milling that made the spores LESS effective as a bioweapon.
There is no principle for coating spores. There is a principle for milling spores that causes spores to end up with a silica coating. A "principle for coating spores" would be a scientific reason for applying a coating of silica to spores to make a more effective bioweapon. There is no such "principle."