Key Definitions
Confined Space per OSHA requires three characteristics:
- Large enough for worker entry and task performance
- Limited or restricted entry/exit
- Not designed for continuous occupancy
Examples include trenches, tanks, vaults, manholes, pipelines, and excavated pits.
PRCS Classification Criteria
A confined space becomes a PRCS when containing one or more hazards:
Atmospheric Hazards:
- Oxygen deficiency (below 19.5%) or enrichment (above 23.5%)
- Flammable gases or vapors
- Toxic substances like hydrogen sulfide or carbon monoxide
Physical Hazards:
- Engulfment risks from soil, sand, or water
- Internal configuration dangers (sloping walls, converging surfaces)
- Mechanical, electrical, or thermal hazards
- Active utilities or unstable ground
OSHA Compliance Requirements (29 CFR 1910.146)
The standard mandates:
- Written Permit System documenting hazards, safety measures, and time limits
- Atmospheric Testing before and during entry with continuous monitoring
- Ventilation to maintain safe air quality and isolate utilities
- Safe Access via ladders, ramps, or steps with exits within 25 feet when possible
- Trained Attendant stationed outside monitoring entrants
- Rescue Procedures including non-entry systems and trained emergency teams
Industry Applications
Common PRCS scenarios in hydro excavation include utility vaults, manholes, excavated shafts exceeding 4 feet depth, and underground storage tanks.
Compliance Importance
Neglecting PRCS standards risks worker fatalities, significant OSHA penalties, project delays, and legal liability.
