Chapter 18: Work Hazards

Oxygen Deficiency & Enrichment
Oxygen Deficiency Definition: Oxygen concentration below 20.8% (ambient concentration). Oxygen deficiency can be expected in confined spaces (e.g., underground storage tanks, valleys, ditches, trenches, basements of building, pipes) and stagnant ponds. OSHA requires supplied air when oxygen concentration is less than 19.5%. Oxygen deficiency is caused by: Consumption by organisms or chemical reactions, especially oxidation (e.g., rust) and fire. Displacement by other gases.
% Oxygen	Physiological Effects of Oxygen Deficiency
19.5 - 16	No visible effects
16 - 12	Increased breathing rate. Accelerated heart beat. Impaired attention, thinking and coordination.
14 - 10	Faulty judgment and poor muscular coordination. Muscular exertion causing rapid fatigue. Intermittent respiration.
10 - 6	Nausea, vomiting, inability to perform vigorous movement, or loss of the ability to move, unconsciousness, followed by death.
< 6	Difficulty breathing. Convulsive movements. Death in minutes.

Oxygen Enrichment Definition: Oxygen concentration > 23.5%. Oxygen enrichment can produce oxidation and increase the potential for fire. See ValuJet Flight 592 example.

Explosion and Fire

May result from:

Mixing of incompatible chemicals to from exothermic reaction.

A spark or flame could be introduced into an oxygen-enriched or flammable atmosphere.

The movement or removal of tanks and drums could agitate shock-sensitive compounds or could release materials stored under high pressure.

Standard Procedures to Reduce the Risk of Explosion and Fire:

Have qualified personnel monitor for explosive atmospheres and flammable vapors.

Keep all potential ignition sources away from an explosive or flammable environment.

Use non-sparking, explosion-proof equipment.

Follow safe practices when performing any task that might result in the agitation or release of chemicals.

Lower Explosive Limit = Lower Flammability Limit, LEL, LFL

The lowest concentration that is explosive. If explosivity level is less than 10% lower explosive limit (LEL), continue monitoring with caution. If level is exceeds 10% of LEL, Withdraw Immediately! OSHA does not permit workers to be in an environment that exceeds 10% of the LEL except for initial assessment.

Ionizing Radiation

The potential for damage is dependent on:

The energy of the radiation

Penetration ability of the radiation

Ionizing ability of the radiation source

Chemical properties of the radiation

Radiation Types

Alpha (a) particles - Can cause significant harm, but have low penetration potential. Personal protective equipment and intensive hygiene provide substantial protection.

Beta (�) particles - Can penetrate better than alpha particles and cause "beta burns" and damage the subsurface blood system. Personal protective equipment and intensive hygiene provide substantial protection.

Gamma (G) waves - Pass easily through clothing, PPE and human tissue. Can cause serious permanent bodily damage. Chemical protective equipment provides little if any protection.

Neutrons - Can generate alpha, beta and gamma waves.

Electromagnetic forces - Unknown! For example, high tension wires and electric blankets.

There is no known safe level of radiation.

If levels of radiation above natural background levels are discovered, a health physicist should be consulted. At levels greater than one rem/ hour, all site activities should cease until the site has been assessed by health physicists.

Radiation Measurement

The energy of the radiation is measured in rads (an abbreviation for radiation absorbed doses). However, because rads are not equal in their biological damage potential, they are converted into rems (an abbreviation for roentgen equivalent for man) which represents the potential for damage to human tissue. For gamma rays and beta particles, 1 rad of exposure results in 1 rem. of dose. For alpha particles, 1 rad of exposure results in approximately 20 rem of dose. For neutrons, 1 rad of exposure results in approximately 10 rem of dose.

The chemical properties of the radiation refers to the ability of the radiation-producing chemical to be incorporated into the body. (e.g., because Strontium is similar to Calcium it is readily incorporated into bones).

Electrical Hazards

Safe Work Practices for Electrical Equipment

Maintain all equipment properly.
Use safety features like three-prong plugs, double-insulated tools, and safety switches.
Install or repair only if you are qualified and authorized to do so.
Keep electric cables and cords clean and free from kinks. Never carry equipment by its cords.
Use extension cords only when flexibility is necessary.
Do not touch water, damp surfaces, ungrounded metal, or any bare wires if you are not protected.
Do not wear metal objects when working with electricity.
If you are working near overhead power lines of 50 kilo-Volts or less, no equipment may come any closer than 10 feet from the lines. Add 4 inches for every 10 kilo-Volts over 50 kilo-Volts.

Lockout / Tagout

Designed to remove the risk of:

Accidental start-up

Electrical shock

Release of stored, residual, or potential energy, including Electrical, Mechanical, Pneumatic (i.e., gases, especially air), Hydraulic (involving fluids, especially water), Chemical, Thermal, Water under pressure (or steam), and Gravity

Lockout: The process of blocking the flow of energy from a power source to equipment by locking out a lock, block, or chain that keeps a switch, valve, or lever in the off position.

Tagout: The placement of a tag or other prominent warning device on an energy isolation device to indicate the equipment being controlled may not be operated until the tagout device is removed.

Used in combination with a lockout device unless the employer can demonstrate that the utilization of a tagout system will provide full employee protection.

The tagout device must be non-reusable, attached by hand, self-locking, and non-releasing with a minimum unlocking strength of no less than 50 pounds and must be at least equivalent to a nylon cable tie.

Lockout / Tagout Program

Affected employers must develop written energy control programs that clearly and specifically explain all procedures for lockout / tagout, including:

The intended use of the procedure

Sequence to place, remove, and transfer lockout or tagout devices and who is responsible for them

Steps to test a machine or equipment to make sure it is locked or tagged out

Noise Hazards
Permissible Noise Exposures
Noise Level (Decibels) (dBA)	Duration (Hours / day) (Slow response)
90 92 95 97 100 102 105 110 115	8 6 4 3 2 1� 1 � �
When daily noise exposure is composed of two or more periods of noise exposure of different levels, their combined effect should be considered, rather than the individual effect of each. If the sum of the following fractions: C₁/T₁ + C₂/T₂ + ..... C_n/ exceeds unity (1), then, the mixed exposure should be considered to exceed the limit value. Cn indicates the total time of exposure at a specified noise level, permitted at that noise level; T_n indicates the amount of time allowed at that noise level. For example, suppose a worker is exposed to a noise level of 90 dBA for 4 hours and 98dBA for 1.5 hours. Our equation will be 4 hours (the duration of the first noise exposure) divided by 8 hours (the maximum time exposure allowed for 90 dBA) plus 1.5 hours (the duration of the second noise exposure) divided by 2 hours (the maximum time exposure allowed for 98 dBA). The maximum exposure for 97 is 3 and the maximum exposure for 100 is 2; however, we always round up to the next higher noise level (that is, round 98 up to 100), and use the duration for that noise level (in this case, 2). So, our equation is: 4/8 + 1.5/2 = .5 + .75 = 1.25, which is greater than 1. Therefore, the permissible noise exposure has been exceeded! Question: Would the employee have been in compliance if he / she had worn earmuffs during the 1.5 hours when the noise level was 98 dBA? (Typical earmuffs lower the noise level 32 dBA.) Answer: Because the earmuffs lowered the noise level from 98 dBA to 66 dBA, 66 dBA is below the regulated noise level. Therefore, our new equation is 4/8 (which is unchanged) + 0/0 which is .5 which is < 1. Therefore, the employee is now in compliance by wearing earmuffs for 1.5 hours during the noisy part of the day.
Noise Action Level If the 8-hour time weighted average noise exposures equal or exceed 85 dBA, an audio testing program, hearing protectors and a training program must be implemented, with annual refresher. As a general rule of thumb, if an individual’s voice must be raised to converse at a distance of three feet, the noise level probably exceeds 85 dBA.

Threshold Limit Values for Impulsive or Impactive Noises
Sound Level dB	Permitted Number of Impulses or Impacts per Day
140 130 120	100 1000 10,000

Confined Spaces

General Definitions

OSHA Definition (29 CFR 1910: General Industry): Means a space that is large enough and so configured that an employee can bodily enter and perform assigned work; and has limited or restricted means for entry or exit (for example, tanks, vessels, silos, storage bins, hoppers, vaults, and pits are spaces that may have limited means of entry.); and is not designed for continuous employee occupancy.

OSHA Definition (29 CFR 1926: Construction): Means any space having a limited means of egress, which is subject to the accumulation of toxic or flammable contaminants or has an oxygen deficient atmosphere. Confined or enclosed spaces include, but are not limited to, storage tanks, process vessels, bins, boilers, ventilation or exhaust ducts, sewers, underground utility vaults, tunnels, pipelines, and open top spaces more than 4 feet in depth such as pits, tubs, vaults, and vessels.

NIOSH Definition (Publication No. 80-106): Refers to a space which by design has limited openings for entry and exit: unfavorable natural ventilation which could contain or produce dangerous air contaminants, and which is not intended for continuous employee occupancy. Confined spaces include but are not limited to storage tanks, compartments of ships, process vessels, pits, silos, vats, degreasers, reaction vessels, boilers, ventilation and exhaust ducts, sewers, tunnels, underground utility vaults, and pipelines.

Types of Confined Spaces

Non-permit-required Confined Spaces (not regulated by OSHA)

Permit-required Confined Spaces (are regulated by OSHA in 29 CFR 1910.134)

Permit-required Confined Spaces

Have one or more of these characteristics:

Contains or has a potential to contain a hazardous atmosphere

Contains a material that has the potential for engulfing an entrant,

Has an internal configuration such that an entrant could be trapped or asphyxiated by inwardly converging walls or by a floor which slopes downward and tapers to a smaller cross-section,

Contains any other recognized serious safety or health hazard (e.g., unguarded openings, high or low temperatures, poor illumination, sharp edges, steam, compressed gases and liquids, flammable or combustible materials, and mechanical or electrical exposures.)

Why are Confined Spaces Dangerous?

By-products of previously stored materials or chemicals can often leach back out of the walls, changing the composition of the confined space environment.

Accidental leaks of spills can create a variety of hazards within a confined space, including fumes, vapors, explosions, or increase the likelihood of "slip, trip and fall" accidents.

Chemical reactions from cleaning solutions.

Oxidation such as rusting of metals or the rotting, decomposition and fermentation of organic materials can deplete oxygen levels.

Mechanical operations such as welding, painting, cleaning, scraping or sandblasting can generate confined space hazards.

Inerting activities such as using non-flammable products like carbon dioxide, helium and nitrogen may displace oxygen within a confined space.

Confined Space Program

The permit space entry program must:

Identify and evaluate permit space hazards before entry.

Establish and implement means to prevent unauthorized entry.

Establish and implement means to eliminate or control hazards necessary for safe entry by:
- Purging, inerting, flushing or continuously ventilating the permit space as necessary to eliminate or control atmospheric hazards.
  - If ventilation alone can make a confined space safe for entry, then one only needs to comply with the requirements of 29 CFR 1910.146(c)()(i) and ii), otherwise, one needs to comply with all sections of 29 CFR 1910.146.

Provide, maintain, and require the use of personal protective equipment necessary for safe entry.

Require testing of atmospheric conditions inside the space before entry. Tests must be conducted for the presences of a hazardous atmosphere (a confined space atmosphere that may expose employees to the risk of death, incapacitation, impairment of ability to self-rescue from one or more of the following causes:
- Flammable gas, vapor, or mist in excess of 10% of its lower flammable limit (LFL).
- Airborne combustible dust at a concentration that meets or exceeds its LFL (approximated as a condition in which the dust obscures vision at a distance of 5 feet or less).
- Atmospheric oxygen concentration < 19.5 % or > 23.5 %.
- Atmospheric concentration of any substance > its permissible exposure limit.
- Any other atmospheric condition that is immediately dangerous to life or health.

Ensure that at least one attendant is stationed outside during entry.

Coordinate with any contractors used.

Implement rescue procedures.

Establish, in writing, the permit system.

Review the program annually.

Additional OSHA Regulations (not addressed elsewhere)

Fixed Industrial Stairs
Fixed Ladders
Safety Requirements for Scaffolding
Employee Emergency Plans and Fire Prevention Plans
Eye and Face Protection
Occupational Head Protection
Occupational Foot Protection
Medical Services and First Aid
Employee Alarm Systems
Derricks
Welding, Cutting, and Brazing
Ventilation
Fire Prevention
Accident Prevention Signs and Tags
Hand Tools
Specific Excavation Requirements

OLTRAIN^� is a federally registered trademark of Richard Chinn Environmental Training, Inc.

Illumination Requirements of Construction Sites
Operation	Illumination (foot candles

General site areas	5
Excavation and waste areas, access ways, active storage areas, loading platforms	3
Refueling and field maintenance areas	5
Indoors, warehouses, corridors, hallways & exits	5
Tunnels, shafts and general underground ward areas (Exception: Minimum of 10 foot-candles is required at tunnel and shaft heading during drilling, mucking and scaling).	5
General shops (e.g. mechanical and electrical equipment rooms, active storerooms, barracks or living quarters, locker or dressing rooms, dining areas, and indoor toilets and workrooms.)	10
First aid stations, infirmaries, and offices.	30