The decision this case can inform
Use this record when shutdown work changes fan states or can reverse contaminant flow through a connected kiln, precipitator, duct, or enclosure.
NIOSH health-hazard evaluation with a reproduced shutdown condition and direct measurements. Concentrations and flow paths are configuration-specific.
What the public record actually establishes
- F1
Maintenance workers reported a bleach-like odor with eye and respiratory irritation during kiln shutdown work.
- F2
NIOSH reproduced the condition and attributed it to ozone from the electrostatic precipitator backdrafting while the induced-draft fan was off.
- F3
Ozone measured 0.6–0.7 ppm in recreated conditions and above 0.7 ppm at a rear portal.
- F4
A direct-reading instrument recorded 4.5 ppm in the evaluated configuration.
Facts and reported results are kept separate from the lesson a plant may choose to test.
Operating context
Kiln maintenance personnel reported a bleach-like odor and eye and respiratory irritation during shutdown.
Intervention or finding
NIOSH reproduced the condition and concluded ozone from the electrostatic precipitator backdrafted when the induced-draft fan was off.
Documented result
Ozone measured 0.6-0.7 ppm in recreated conditions, above 0.7 ppm at a rear portal, and 4.5 ppm on a direct-reading meter.
Plant interpretation
Evaluate connected-equipment contaminant migration for every shutdown ventilation state before entry.
Transfer boundary
Concentrations are configuration-specific and cannot be transferred to another plant.
Questions to verify at your plant
These are decision checks, not operating instructions. Resolve them through local risk assessment, technical review, and authorization.
- 01
For each shutdown state, where can contaminants migrate when normal pressure relationships disappear?
- 02
Which connected sources remain energized or chemically active after process shutdown?
- 03
Are ventilation states, atmospheric testing locations, and entry criteria defined for maintenance—not only production?
- 04
What indication would warn workers that flow has reversed or a contaminant has entered the work zone?