In the ready-mix concrete industry, workers may occasionally be required to enter confined spaces—including drum mixers, aggregate bins, silos, pits, washout basins, or maintenance vaults. These spaces can pose serious safety hazards, such as oxygen deficiency, toxic gas buildup, or entrapment risks.
What Is a Confined Space?
A confined space has all three of the following:
- Large enough to enter and perform work
- Limited or restricted entry or exit
- Not designed for continuous worker occupancy
Examples: the inside of a concrete mixer drum, slurry tanks, or below-grade equipment vaults.
Key Safety Considerations:
- Atmospheric Testing
- Always test the air before entering; look for oxygen levels, toxic gases (like carbon monoxide), and flammable vapors.
- Test all areas of the space, not just near the opening.
- Ventilation
- Use forced air ventilation to keep fresh air circulating.
- Retest the atmosphere after ventilation and before entry begins.
- Isolation & Lockout
- Lock out all energy sources connected to the space:
- Electrical (motors, mixers)
- Pneumatic or hydraulic systems
- Fuel valves or agitators
- Required PPE
- Based on the hazard, you may need:
- Respiratory protection (air-purifying or supplied air)
- Protective clothing, gloves, and hard hats
- Fall protection when entering vertical spaces
- Permits & Procedures
- Determine if the confined space is permit-required (has serious hazards like engulfment or toxic atmosphere).
- Non-permit spaces still require safety procedures and oversight.
- Rescue & Standby
- Always have a trained attendant outside the space.
- Rescue equipment must be ready and personnel trained in emergency response.
Never enter a confined space alone or without a communication plan.