In this case an electric shop vacuum that is not approved for hazardous locations was used to clean up Class II Combustible Dust.
https://www.osha.gov/ooc/citations/UngererCompany_1116984.pdf
OSHA citations related to combustible dust hazards
- Combustible dusts shall be collected into an adequately designed collection system
- Good Housekeeping Program Controls Combustible Dust Hazards