Page 252 - Safety Memo

3. An employee entering a bell-bottom pier hole or other 2. No source of ignition is permitted indoors or outdoors
deep or confined-footing excavation shall wear a harness where vapor or gas concentrations may reasonably be
that has a lifeline attended by another employee. expected to exceed 25% of the LEL. 5416(c)
1541(g)(2)(B)
3. Employers need to be aware that most flammable vapors
4. Shafts in other than hard, compact soil shall be are toxic even at a very low concentration and can cause
completely lagged and braced. 1542(c)(1) adverse health effects. Employers must have control
measures to keep employees safe.
5. Head protection is required for workers who enter a well
or shaft. 3381 Note: Check also for confined space conditions and
hazardous locations. 5158, 2540.1, Confined Spaces
6. Shafts more than 20 ft. deep are subject to the TSOs. section of this guide.
8403(a)
7. Provide mechanical exhaust ventilation system and
forced air blower or both for shafts 20 ft. or less which Fall Protection
employees enter and where hazardous atmosphere
exists or reasonably expected to exist due to internal T8 CCR includes fall protection standards in various sections of the
combustion engine operation. 1533(b) GISOs, CSOs, TSOs, and ESOs. These standards reflect the
levels of the fall hazards associated with each activity.
Explosion Hazards A. The factors affecting the level of hazard include the following:
1. Fall height
At times, employees may be exposed to explosion hazards
without their knowledge. In addition to substances (such as 2. Level of hazard awareness and skill of the employee
dynamite) that are designed specifically for the purpose of 3. Physical work environment (e.g., conditions affecting the
creating explosions, there are substances that will cause an stability of the employee on the work surface)
explosion when present in certain concentrations and exposed
to an ignition source. SOs to control these hazards include: 4. Duration of exposure to the fall hazard
A. Combustible dust: Note: Because factors 2, 3, and 4 listed above vary
with different trades and activities, the regulatory
1. Combustible dust concentrations must be controlled at requirements for fall protection reflect those differences.
or below 25% of the lower explosive limit (LEL) unless Below find definitions and selected fall protection
all ignition sources are eliminated or identified and requirements:
specifically controlled. 5174(a)
B. A personal fall protection (PFP) system prevents a worker
2. Accumulated and settled combustible dusts must be from falling or—if the worker is falling—stops the fall.
cleaned up to prevent a fire or explosion. 5174(b) PFP systems include guardrails, safety nets, personal fall
3. Cleaning with compressed air and blowing combustible restraint systems, personal fall arrest systems, and
dust may be done only when other methods cannot positioning device systems.
be used, when possible sources of ignition have been 1. Guardrails are required to guard the open sides of all work
eliminated, and when hoses and nozzles are grounded. surfaces that are 7 1/2 ft. or higher or workers must be
5174(f) protected by other means. The railing must be made from
B. Flammable vapors: select lumber (Doug Fir#1 or better, 1500 psi or
equivalent) and must consist of a top rail 42 inches to 45
1. Ventilation in enclosed places must be sufficient to inches high, 2" x 4" (min.); a 1" x 6" mid-rail halfway
prevent flammable vapor or gas concentrations from between the top rail and the floor; and support posts at least
exceeding 25% of the LEL. 5416(a) 2" x 4" at 8 ft. o.c.
2. A personal fall restraint (PFR) system is used to prevent
an employee from falling. It consists of anchorages,

62 Cal/OSHA Pocket Guide for the Construction Industry | June 2019 Cal/OSHA Pocket Guide for the Construction Industry | June 2019 63