In a recent Q&A on the FacilityCare website, consultant Brad Keyes answered a question about dust on sprinkler heads.
Q: I just had a survey and received a finding for dust on some of the sprinkler heads. I understand that foreign material is not permitted, but minute amounts of dust??
A: Dust is a foreign material, and foreign material is not permitted on sprinkler heads. I support the finding, since how much dust is too much? If you allow just a little dust, then at what point is it too much dust? Besides, any foreign material, including dust, can change the reaction time of a sprinkler head.
Why Healthcare Facilities Management Is Critical to Patient Safety 
Sanford Health and North Memorial Health Finalize Partnership
Cornerstone Behavioral Healthcare Falls Victim to Ransomware Attack
Containing Candida Auris Across the Care Continuum
Early Entry: Manager's Critical Role in Construction Planning