www.osha.gov

Underground Construction

(Tunneling)

OSHA 3115-06R 2003
This informational booklet provides a 

general overview of a particular topic 

related to OSHA standards. It does not alter

or determine compliance responsibilities in

OSHA standards or the Occupational Safety

and Health Act of 1970. Because interpretations and enforcement policy may change

over time, you should consult current OSHA

administrative interpretations and decisions

by the Occupational Safety and Health

Review Commission and the Courts for 

additional guidance on OSHA compliance

requirements.

This publication is in the public domain 

and may be reproduced, fully or partially,

without permission. Source credit is 

requested but not required.

This information is available to sensory

impaired individuals upon request.

Voice phone: (202) 693-1999; teletypewriter

(TTY) number: (877) 889-5627.


Underground Construction 

(Tunneling)

U.S. Department of Labor

Elaine L. Chao, Secretary

Occupational Safety and Health Administration

John L. Henshaw, Assistant Secretary

OSHA 3115-06R

2003
Contents

Introduction...4

Construction operations covered by 

the OSHA standard...4

Employers and employees covered by 

the OSHA standard...5

Requirements of the OSHA standard...6

The need for a “competent person”...6

Training requirements...6

Notification and communication requirements...7

Site control procedures...8

Check-in/check-out procedures...8

Control of access and egress...9

Ground support of portal and subsidence areas...9

Ground support of underground areas...9

Ground support of shafts...10

Fire prevention and control...10

Ventilation requirements...12

Illumination requirements...13 

Special air monitoring requirements...13

Test for oxygen first...14

Testing for methane and other flammable gases...14

Hydrogen sulfide levels...15

Special conditions for drilling and 

blasting underground...15

2
Special requirements for using cranes 

and hoists underground...16

Potential hazards that require special precautions...18

Gassy or potentially gassy operations...18

Emergency procedures...21

Recordkeeping requirements...22 

OSHA assistance...22

Safety and health management system guidelines...22

State programs...23

OSHA consultation services...23

The OSHA Voluntary Protection Program (VPP)...24

Strategic Partnership Programs...25

The OSHA Alliance Program...25

OSHA training and education...26

Information available electronically...26

OSHA publications...27

Contacting OSHA...27

OSHA Regional Offices...28

3


Introduction

The construction of underground tunnels, shafts, chambers, and

passageways are essential yet dangerous activities. Working under

reduced light conditions, difficult or limited access and egress, with

the potential for exposure to air contaminants and the hazards of

fire and explosion, underground construction workers face many

dangers. To help employers protect the safety and health of underground construction workers, the Occupational Safety and Health

Administration (OSHA) has prepared a number of guidance

documents, including the underground construction regulations,

found in Part 1926, section 800 of Title 29 of the Code of Federal

Regulations (29 CFR 1926.800).

OSHA regulations relating to underground construction were

originally adopted in 1971 and revised over the years to add new

protective measures and enhance worker safety. This publication

summarizes OSHA’s regulations related to underground construction. As such, it should be used as a guide but not as a substitute

for the complete text of 29 CFR 1926.800.

Construction operations covered 

by the OSHA standard

The OSHA underground construction regulation (29 CFR

1926.800) applies to the construction of underground tunnels,

shafts, chambers, and passageways. It also applies to cut-andcover excavations connected to ongoing underground construction

as well as those that create conditions characteristic of underground construction. These hazards include reduced natural ventilation and light, difficult and limited access and egress, exposure to

air contaminants, fire, flooding, and explosion. The regulation does

not apply to excavation and trenching operations for above ground

structures that are not physically connected to an underground construction operation or to underground electrical transmission and

distribution lines.

OSHA has developed the following definitions for construction

activities that fall within the underground construction field:

4
A tunnel is “an excavation beneath the surface of the ground,

the longer axis of which makes an angle not greater than 20

degrees to the horizontal.”

A shaft is “(1) a passage made from the surface of the ground to

a point underground, the longer axis of which makes an angle

greater than 20 degrees to the horizontal; or (2) a pit in which there

are employees, and it is foreseeable that they may enter (or do

enter) the horizontal excavation; or (3) a pit that has typical 

underground construction hazards and is connected to a 

horizontal excavation.”

Employers and employees covered 

by the OSHA standard

In general, OSHA authority extends to all private sector

employers with one or more employees, as well as to civilian

employees in federal agencies. As such, OSHA coverage applies to

employers and employees in the construction industry. Workers

not covered by OSHA include the self-employed; public employees

of state and local governments; employees whose working conditions are regulated by other federal agencies, such as mine workers

and atomic energy workers; and immediate family members of

farming operations that do not employ outside workers.

States can administer their own occupational safety and health

programs through plans approved by the Department of Labor

under section 18(b) of the Occupational Safety and Health (OSH)

Act of 1970, but they must enforce standards that are at least as

effective as federal requirements. In 2003, 26 states operated their

own safety and health programs under approved programs. (See

OSHA’s website at www.osha.gov for a list of those states.) Of

these, 23 states cover both private and public employees while

three states cover only public sector employees. 

State safety and health standards under approved plans 

must either be identical to or at least as effective as federal 

OSHA standards.

5


Requirements of the OSHA standard

The underground construction standard covers many topics of

concern to those who work in the challenging environment of

underground construction. A sampling of items covered by the

standard includes requirements for safe access and egress routes,

employee training in hazard recognition, a “check-in/check-out”

procedure, and emergency procedures. This booklet summarizes

all requirements of the standard.

The standard provides some flexibility in methods to control

workplace hazards in underground construction as long as appropriate precautions are taken to protect workers in a variety of situations. OSHA requires that a “competent person” be responsible for

carrying out several requirements of the underground construction

regulations. Situations that require intervention by a “competent

person” are identified in the following sections.

The need for a “competent person”

The definition of a “competent person” in 29 CFR 1926.32 (f) is

as follows:

One who is capable of identifying existing and predictable

hazards in the surroundings or working conditions which are

unsanitary, hazardous, or dangerous to employees, and who has

authorization to take prompt correctivemeasures to eliminate them.

Under Subpart S, Underground Construction, caissons, cofferdams, and compressed air, a competent person is responsible for

inspecting and evaluating workplace conditions, including air monitoring and the presence of air contaminants, ground stability, and

the drilling, hauling and hoisting of equipment, to identify and

correct any deficiencies.

Training requirements

All employees involved in underground construction must be

trained to recognize and respond to hazards associated with this

type of work. Training should be tailored to the specific requirements of the jobsite and include any unique issues or requirements.

6
The following topics should be part of an underground construction employee training program:

■ Air monitoring and ventilation

■ Illumination

■ Communications

■ Flood control

■ Personal protective equipment

■ Emergency procedures, including evacuation plans

■ Check-in/check-out procedures

■ Explosives

■ Fire prevention and protection

■ Mechanical equipment

Notification and communication 

requirements

Any time an employer receives a notification of a hazardous

condition, all oncoming shifts must be notified of occurrences or

conditions that either have affected or might affect their safety.

Examples of this type of situation include equipment failures, earth

or rockslides, cave-ins, flooding, fires, explosions, or release of gas. 

The employer must also maintain open lines of communication

with other employers at the worksite to ensure a rapid and

complete exchange of information concerning events or situations

that may impact worker safety.

Employers must maintain lines of communication with

employees during underground construction activities. To ensure

effective communications are always available, communication

systems must be tested upon initial entry of each shift to the underground and as often as necessary at a later time to ensure they are

in working order. Powered communication systems must operate

on an independent power supply and be installed so that the use of

or disruption of any single communication device or signal location

will not disrupt the operation of the system in any other location.

7


If natural unassisted voice communication is ineffective at any

time, a power-assisted means must be used to ensure communication between the work face, the bottom of the shaft, and the

surface. In the case of an individual employee working alone

underground in a hazardous location who is out of range of natural

unassisted voice communication and not able to be observed by

other employees, the employer must provide an effective means of

obtaining assistance in the event of an emergency.

All shafts being developed or used for personnel access or

hoisting require two effective means of communication. In

addition, hoist operators must have a closed-circuit voice communication system connected to each landing station, with speakermicrophones located so that the operator can communicate with

individual stations while the hoist is in use. (See the section on

cranes and hoists later in this booklet for more specific information.)

Site control procedures 

Check-in/check-out procedures

The employer must maintain a check-in/check-out procedure to

ensure that above ground personnel maintain an accurate accounting of the number of persons underground and to prevent unauthorized persons from gaining access to the site. This is especially

important in the event of an emergency but is a common sense

requirement at all times. 

The only time this procedure is not required is when an underground construction project designed for human occupancy is

completed to the point that permanent environmental controls are

effective and any remaining construction activity does not have the

potential to create an environmental hazard or structural failure in

the construction area. 

Any time an employee is working underground, at least one designated person must be on duty above ground. This person is

responsible for calling for immediate assistance and keeping an

accurate count of employees who remain underground in the event

of an emergency. 

8


Control of access and egress

In addition to establishing a check-in/check-out procedure, the

employer must ensure safe access to and egress from all workstations at the construction site to protect employees from potential

hazards, such as being struck by excavators, haulage machines, or

other moving equipment. 

To help control access, all unused openings, including chutes

and man ways, must be tightly covered, bulk headed, barricaded,

or fenced off, and posted with warning signs that read, “Keep Out”

or similar language. 

Ground support of portal and subsidence areas

Portal openings and access areas must be guarded by shoring,

fencing, head walls, shotcreting or equivalent protection to ensure

that employees and equipment have a safe means to access these

areas. Subsidence areas must be similarly guarded by shoring,

filling in, or placing barricades and warning signs to prevent entry.

Adjacent areas must be scaled or secured to prevent loose soil,

rock, or fractured materials from endangering portal, subsidence,

and access areas.

Ground support of underground areas

A competent person must inspect the roof, face, and walls of the

work areas at the beginning of each shift and as often as necessary

to ensure ground stability. The competent person tasked with such

inspection responsibilities must be protected from loose ground by

location, ground support, or equivalent means. The ground conditions along all haulage ways and travel ways must also be

inspected as frequently as necessary to ensure safe passage and

loose ground considered to be hazardous to employees must be

scaled, supported, or taken down.

A competent person must determine how often rock bolts need

to be tested to ensure that they meet the necessary torque, taking

into consideration ground conditions, distance from vibration

sources, and the specific bolt system in use. Only torque wrenches

should be used when torsion-dependent bolts are used for ground

support.

9


Employees involved in installing ground support systems must

be adequately protected from the hazards of loose ground. The

bottoms of any support sets installed must have sufficient

anchorage to prevent ground pressures from dislodging the

support base. Lateral bracing (including collar bracing, tie rods, or

spreaders) must be provided between immediately adjacent sets to

increase stability. 

Any dislodged or damaged ground supports that create a

hazardous condition must be promptly repaired or replaced. The

new supports must be installed before removing the damaged

supports. Some type of support, such as a shield, must be used to

maintain a safe travel way for employees working in dead-end

areas ahead of any support replacement operations. 

Ground support of shafts

Shafts and wells more than 5 feet in depth (1.53 m) entered by

employees must be supported by steel casing, concrete pipe,

timber, solid rock, or other suitable material. The full depth of the

shaft must be supported except where it penetrates into solid rock

that will not change as a result of exposure. Where the potential for

shear exists, where the shaft passes through earth into solid rock in

either direction, or where the shaft ends in solid rock, the casing or

bracing must extend at least 5 feet (1.53 m) into the solid rock. 

The casing or bracing must also extend 42 (± 3) inches above

ground level unless a standard railing is installed, the adjacent

ground slopes away from the shaft collar, and barriers exist to

prevent mobile equipment operating near the shaft from jumping

over the bracing. If these conditions are met, the casing or bracing

may be reduced to 12 inches above ground.

Fire prevention and control

In addition to the basic fire prevention and control guidance set

forth in 29 CFR 1926 Subpart F, underground construction operations are subject to several specific requirements. 

Open flames and fires are prohibited in underground construction

areas except as permitted for welding, cutting, or other hot work

operations. Smoking is prohibited unless an area is free of fire and

10


explosion hazards. Signage prohibiting smoking and open flames

should be placed throughout work areas. Fire extinguishers of at

least 4A:40B:C rating or equivalent extinguishing means must be

available at the head and tail pulleys of underground belt

conveyers. 

All underground structures and those within 100 feet (30.48 m)

of an opening to the underground must be constructed of materials

with a fire resistance rating of at least one hour. Also, no

flammable or combustible material may be stored above ground

within 100 feet (30.48 m) of any access point to an underground

operation. If space limitations make this unfeasible, the material

must be positioned as far as possible from the entrance with a fireresistant barrier that has at least a one-hour rating between the

material and the opening. Alternative precautionary measures may

be adopted from industry practices used under similar working 

conditions or measures recommended under industry consensus

standards. A site hazard analysis may be helpful to determine the

effectiveness of precautionary measures. Any spill of flammable or

combustible material must be cleaned up immediately. 

Gasoline may not be underground at any time for any purpose

due to its volatile qualities. Internal combustion engines (except

diesel-powered engines on mobile equipment) are prohibited

underground. Acetylene, liquefied petroleum gas, and methyl

acetylene propadiene stabilized gas may be used underground for

welding, cutting, and other hot work if all requirements of OSHA

regulations pertaining to such activities are met. (See 29 CFR 1926

Subpart J and 29 CFR 1926.800(j)(k)(m)(n) for a complete explanation of these requirements.) Only enough fuel gas and oxygen

cylinders for welding, cutting, or hot work during a 24-hour period

are allowed underground. Noncombustible barriers must be

installed below such activities if they are performed in or over a

shaft or rise.

Oil, grease, and diesel fuel stored underground must be kept in

tightly sealed containers in fire-resistant areas at least 300 feet

(91.44 m) from underground explosive magazines, and at least 100

feet (30.48 m) from shaft stations and steeply inclined passageways. Storage areas must be positioned or diked to ensure that if a

11


container breaks open, any fluids will not flow out of the storage

area. Any hydraulically-actuated underground machinery must use

fire-resistant hydraulic fluids unless it is protected by a fire suppression system or multi-purpose fire extinguisher rated at least

4A:40B:C and of sufficient capacity for the type and size of

equipment involved. 

Several specific requirements apply to the use of diesel fuel in

underground construction operations, as follows:

■ A surface level tank holding diesel fuel to be pumped to an 

underground storage site must have a maximum capacity no 

greater than the amount of fuel required to supply underground 

equipment for 24 hours.

■ A surface level tank must be connected to the underground 

fueling station by an acceptable pipe or hose system controlled 

at the surface by a valve and at the bottom by a hose nozzle.

■ The transfer pipe must remain empty at all times except when 

transferring diesel fuel.

■ All hoisting operations in the shaft must be suspended during 

refueling operations if the supply piping in the shaft is not 

protected from potential damage.

Ventilation requirements

Fresh air must be supplied to all underground work areas in sufficient amounts to prevent any dangerous or harmful accumulation

of dusts, fumes, mists, vapors, or gases. If natural ventilation does

not provide the necessary air quality through sufficient air volume

and air flow, the employer must provide mechanical ventilation to

ensure that each employee working underground has at least 200

cubic feet (5.7m3) of fresh air per minute. 

When performing work that is likely to produce dust, fumes,

mists, vapors, or gases (such as blasting or rock drilling), the linear

velocity of air flow in the tunnel bore, shafts, and all other underground work areas must be at least 30 feet (9.15 m) per minute.

When such operations are complete, the ventilation systems must

exhaust smoke and fumes to the outside atmosphere before

12


resuming work in all affected areas. When drilling rock or concrete,

dust control measures such as wet drilling, vacuum collectors, and

water mix spray systems must be used to maintain dust levels

within limits set in 29 CFR 1926.55, which includes gases, vapors,

fumes, dusts, and mists. 

The direction of mechanical airflow must be reversible but ventilation doors must be designed and installed to remain closed when

in use, regardless of the direction of the airflow. If the ventilation

system has been shut down and all employees are removed from

the underground area, only competent persons authorized to test

for air contaminants may be allowed underground until the ventilation system has been restored and all affected areas have tested at

acceptable limits for air contaminants.

Illumination requirements 

As in all construction operations, OSHA requires that proper illumination be provided during tunneling operations (see 29 CFR

1926.56 for details). When explosives are handled, only acceptable

portable lighting equipment may be used within 50 feet of any

underground heading. 

For general tunneling operations, a minimum illumination

intensity of 5 foot-candles must be maintained, although 10 footcandles must be provided for shaft heading during drilling,

mucking, and scaling. 

Special air monitoring requirements

The employer must assign a “competent person” to perform air

monitoring. If this individual determines that air contaminants may

present a danger to life at any time, the employer must immediately take all necessary precautions and post a notice at all entrances

to the underground site about the hazardous condition.

In performing air monitoring duties, the competent person must

take into consideration the location of the jobsite (its proximity to

fuel tanks, sewers, gas lines, etc.); the geology of the site, including

soil type and permeability; the history of the site and the construc13


tion operation (changes in levels of substances monitored over

time); and work practices at the jobsite (use of diesel engines,

explosives, and fuel gas; hot work, welding, and cutting; and the

physical reactions of employees to working underground.

Test for oxygen first 

The competent person charged with air monitoring must test for

oxygen content before testing for air contaminants. All underground work areas must be tested as often as necessary to verify

that the atmosphere at normal atmospheric pressure remains

within the acceptable parameters of 19.5 and 22 percent oxygen.

After verifying oxygen levels, the competent person must test all

underground work areas for carbon monoxide, nitrogen dioxide,

hydrogen sulfide, and other toxic gases, dusts, vapors, mists, and

fumes as often as necessary to ensure that levels remain within

permissible exposure limits (see 29 CFR 1926.55 for detailed 

information on these limits). 

Testing for methane and other flammable gases

The competent person must also test all underground work

areas for methane and other flammable gases to determine

whether the operation must be classified as potentially gassy or

gassy. If the atmosphere meets the criteria for these designations,

the precautions listed in the section discussing gassy or potentially

gassy operations later in this booklet must be followed. Other 

precautions to take when testing for methane or other flammable

gases include:

■ If 20 percent or more of the lower explosive limit for methane or

other flammable gases is detected in any underground work 

area or in the air return, all employees must be evacuated to a 

safe location above ground (except those employees required to

eliminate the hazard). Electrical power (except for acceptable 

pumping and ventilation equipment) must be cut off to the area 

until concentrations reach less than 20 percent of the lower 

explosive limit.

■ If 10 percent or more of the lower explosive limit for methane 

gas or other flammable gases is detected near any welding, 

14


cutting, or other hot work, the work must be suspended until the

concentration is reduced to below 10 percent of the lower 

explosive limit.

■ When 5 percent or more of the lower explosive limit for 

methane or other flammable gases is detected in an underground work area or in the air return, steps should be taken to 

increase ventilation air volume or otherwise control the gas 

concentration (unless all requirements of operating under 

potentially gassy or gassy operations are met). 

Hydrogen sulfide levels

When air monitoring reveals the presence of 5 ppm or more of

hydrogen sulfide, the affected underground areas must be tested at

the beginning and midpoint of each shift until the concentration is

measured at less than 5 ppm for three consecutive days. 

Employees must be notified if hydrogen sulfide is detected in

amounts exceeding 10 ppm and a continuous sampling and indicating monitor must be used to keep track of levels. If the concentration of hydrogen sulfide reaches 20 ppm, the monitor must be

designed to provide both visual and audible alarms to warn that

additional measures (respirator use, increased ventilation, evacuation) may be appropriate.

Special conditions for drilling 

and blasting underground

Before initiating any drilling operation underground, a

“competent person” must inspect all drilling and associated

equipment as well as the drilling area and correct any hazards.

Employees are not allowed on a drill mast when a drill bit is in

operation or a drill machine is being moved. Also, when moving a

drill machine, all associated equipment and tools must be secured

and the mast placed in a safe position.

Working on or around jumbo decks involves special safety 

precautions, including the following:

■ Locate all receptacles or racks to store drill steel on jumbos.

15


■ Warn employees working below jumbo decks when drilling is 

about to begin.

■ The top deck of a jumbo must have a mechanical way to lift 

unwieldy or heavy items.

■ Only employees assisting the operator may ride on the jumbo 

unless it is equipped with seating for each passenger and 

protection from crushing or catching hazards. 

■ Jumbo decks more than 10 feet high must be equipped with 

guardrails on all open sides unless an adjacent surface provides 

fall protection. Jumbo decks and stair treads must be slipresistant, secured, and maintained to prevent slip, trip, and 

fall hazards.

■ Jumbos must be chocked so they will not move when 

employees are working on them.

Whenever an underground blasting operation in a shaft is

complete, a “competent person” must check the air quality and

make sure that no walls, ladders, timbers, blocking, and wedges

have been loosened as a result of the activity. If repairs are

required, only employees involved in repair activity may be in or

below affected areas until repairs are complete.

All blasting wires must be kept clear of electrical lines, pipes,

rails and other conductive material (except earth), to prevent explosions or exposure of employees to electric current.

Special requirements for using 

cranes and hoists underground

The OSHA standard has provisions for the use of cranes or

hoists that are unique to underground construction. In addition to

provisions that apply to all construction activities using cranes or

hoists (29 CFR 1926.550 and 29 CFR 1926.552), cranes used in

underground construction must be equipped with a limit switch to

prevent overtravel at the top and bottom of the hoist way. The limit

switch should only be used when operational controls malfunction.

Hoist controls must be arranged so the operator can reach all

16


controls and the emergency power cutoff without reaching beyond

his/her normal operating position.

Underground hoists must be designed to allow powering of the

hoist drum in both directions and so that brakes are automatically

applied upon power release or failure. The hoist operator must

have a closed-circuit voice communication system with speaker

microphones to communicate with individual landing stations.

Also, hoists must be equipped with landing level indicators

(marking the hoist rope is not adequate) and fire extinguishers

(rated at least 2A:10B:C) in each hoist house.

Before using a hoist that has been out of operation for a

complete shift or after repair or service, the operator must test run

the equipment and correct any unsafe conditions before use.

Inspections and load testing to 100 percent of capacity must be

performed at least annually and after any repairs or alterations

affecting the structural integrity of the hoist. 

For material hoists, wire rope used in load lines must support at

least five times the maximum intended load or the factor recommended by the rope manufacturer, whichever is greater. Personnel

hoists must have at least two means to stop the load, each able to

stop and hold 150 percent of the hoists’ rated line pull. For

personnel hoisting, a broken-rope safety, safety catch, or arrestment device are not adequate means of stopping. 

Other aspects of hoist safety that apply to underground construction include:

■ Employees may not ride on top of any cage, skip, or bucket 

unless inspecting or maintaining the system and wearing a 

safety belt or harness.

■ Personnel and materials must be hoisted separately (except 

small tools and supplies secured in a nonhazardous manner).

■ When sinking shafts 75 feet (22.86 m) or less, cages, skips, and 

buckets that may swing, bump, or snag against shaft sides must 

be guided by fenders, rails, ropes, or a combination. If the shaft 

is more than 75 feet, hoisted objects must be rope- or railguided for the full length of travel.

17


Additional safety requirements for personnel hoists in underground operations include:

■ The operator must be able to see and hear signals at the 

operator’s station.

■ All cages must be equipped with a steel-plate protective canopy 

that slopes to the outside and can be pushed up for emergency 

egress and have a locking door that opens only inward. 

■ The sides of personnel cages must be enclosed by 1/2 inch wire 

mesh to a height of at least 6 feet (1.83 m). If the cage is being 

used as a work platform and is not in motion, the sides may be 

reduced to 42 inches (1.07 m). 

■ During sinking operations in shafts where guides and safeties 

are not used, the personnel platform may not exceed 200 feet 

(60.96 m) per minute and governors must be used during 

personnel hoisting. The speed may increase to 600 feet 

(182.88 m) per minute when guides and safeties are used and 

greater speeds when shafts are complete.

Potential hazards that require 

special precautions 

Gassy or potentially gassy operations

Gassy or potentially gassy operations present specific hazards to

underground construction workers. It is essential that employers

understand the terms “gassy” and “potentially gassy” and to know

what precautions to take when dealing with such environments.

Operations that meet the criteria for this hazardous classification

must be equipped with ventilation systems constructed with fireresistant materials; have acceptable electrical systems, including

fan motors; and have above ground controls to reverse the air flow.

When using a mine-type ventilation system with an offset main fan

on the surface, the system must be equipped with explosion doors

or a weak-wall with an area at least equivalent to the crosssectional area of the airway. 

18


Gassy operations occur under the following conditions:

■ When air monitoring discloses 10 percent or more of the lower 

explosive limit for methane or other flammable gases measured 

at 12 inches (304.8 mm) ± 0.25 inch (6.35 mm) from the roof, 

face, floor, or walls in any underground work area for three 

consecutive days; or

■ There has been an ignition of methane or other flammable 

gases emanating from the strata that indicates the presence of 

such gases; or

■ The underground construction operation is connected to an 

underground work area classified as gassy and subject to a 

continuous course of air that contains the flammable gas 

concentration. 

The underground construction standard requires that gassy

operations meet several special requirements, including both

personnel and equipment safety concerns. These requirements

include:

■ Entrances to a gassy operation must be marked with 

prominently posted signage that identifies the area as gassy.

■ Maintain a fire watch when performing hot work (welding, 

cutting, heating) in a gassy area and for a sufficient period after 

completing the work to ensure no possibility of fire remains. 

(See 29 CFR 1926.352(e))

■ Use only acceptable equipment in well-maintained condition. 

Any mobile diesel-powered equipment must either be approved 

by MSHA and meet the requirements of 30 CFR part 36 

(formerly Schedule 31) or the employer must demonstrate that 

the equipment is fully equivalent to MSHA-approved equipment 

and operated according to these regulations. 

■ Smoking is prohibited in all gassy operations; the employer 

must collect all possible sources of ignition (matches, lighters, 

etc.) from any person entering a gassy operation area.

■ All operations in the affected area must stop when an operation 

is classified as gassy until full compliance with gassy operation 

requirements is confirmed or the operation is downgraded to a 

potentially gassy operation (see the following section). The only

19


exceptions are operations to control the gas concentration, 

installation of above ground equipment to reverse the airflow,

or actions to comply with gassy operation requirements.

Gassy operations can be downgraded to potentially gassy when

air monitoring results remain below 10 percent of the lower

explosive limit for methane or other flammable gases for three consecutive days.

Potentially gassy operations, such as an unexpected pocket of

gas, occur when the following conditions exist:

■ Air monitoring shows 10 percent or more of the lower explosive 

limit for methane or other flammable gases measured at 12 

inches (304.8 mm) ± 0.25 inch (6.35 mm) from the roof, face, 

floor or walls in any underground work area for more than a 24-

hour period. 

■ The history of the geographical area, geological formation, or 

past experience indicates that 10 percent or more of the lower 

explosive limit for methane or other flammable gases is likely to 

be encountered in such underground operations.

Both gassy and potentially gassy operations require special air

monitoring actions under the guidance of a “competent person,”

including testing for oxygen and flammable gas content in the

affected underground work areas and adjacent work areas at the

beginning and midpoint of each work shift. A manual flammable

gas monitor should be used for gas testing and a manual electrical

shut down control must be provided near the heading for the gas

monitor.

The use of rapid excavation machines requires continuous

automatic flammable gas monitoring to monitor the air at the

heading, on the rib, and in the return air duct. If 20 percent or more

of the lower explosive limit for methane or other flammable gases

is encountered, the continuous monitor alert should signal the

heading and shut down electrical power in the affected underground work area (except for required pumping and ventilation

equipment). 

Local gas tests must be conducted before and throughout

welding, cutting or other hot work. In underground operations

20


driven by drill-and-blast methods, the air in the affected area

must be continuously tested for flammable gas when employees

are working in the area as well as before reentering after 

blasting operations.

Emergency procedures

Whenever an employee is working underground at least one

designated person must be on duty above ground, responsible for

maintaining an accurate count of the number of employees underground and summoning emergency aid if needed. Every employee

working underground must have a portable hand lamp or cap lamp

for emergency use unless natural light or an emergency lighting

system provides adequate illumination for escape. Employers must

provide self-rescuers approved by the National Institute for

Occupational Safety and Health (NIOSH) in all underground work

areas where employees might be trapped by smoke or gas. (See

CFR 1926.103 for more information.)

If 25 or more employees work underground at one time, the

employer must provide at least two 5-person rescue teams, one at

the jobsite or within 30 minutes travel time from the entry point to

the site and the other team within two hours travel time. If less

than 25 employees work underground, the employer must have

one 5-person rescue team at the jobsite or within 30 minutes travel

time. In both situations, advance arrangements can be made for

local rescue services to meet this requirement. Rescue team

members must be trained in rescue procedures, the use and limitations of breathing apparatus, and the use of firefighting equipment

with qualifications reviewed annually. When flammable or noxious

gases are anticipated at a jobsite, rescue teams must practice using

self-contained breathing apparatus once a month. The rescue

teams must be available through the duration of a construction

project. 

If a shaft is used as the means of egress, the employer must

arrange for a readily available power-assisted hoisting capability in

case of emergency, unless the regular hoisting means will function

in the event of a power failure. 

21


Recordkeeping requirements 

Records of all air quality tests must be maintained above ground

at the worksite and be available on request to the Secretary of

Labor or his or her representative. The record must include the

location, date, time, substance and amount monitored. Records of

exposures to toxic substances must be kept for 30 years. (See 29

CFR 1910.1020 for more detailed information on access to

employee exposure and medical records.) All other air quality test

records must be retained until the project is complete. 

Inspection certification records for all hoist equipment indicating

the date of the most recent inspection and load-test, the signature

of the person performing the inspection and test, and a serial

number or other identifier for the hoist must be maintained on file

until the project is complete. 

OSHA assistance 

OSHA can provide extensive help through a variety of

programs, including technical assistance about effective safety and

health programs, state plans, workplace consultations, voluntary

protection programs, strategic partnerships, and training and

education, and more. An overall commitment to workplace safety

and health can add value to your business, to your workplace, and

to your life.

Safety and health management 

system guidelines

Effective management of worker safety and health protection is

a decisive factor in reducing the extent and severity of work-related

injuries and illnesses and their related costs. To assist employers

and employees in developing effective safety and health programs,

OSHA published recommended Safety and Health Program

Management Guidelines (Federal Register 54 (16): 3904-3916,

January 26, 1989). These voluntary guidelines can be applied to all

places of employment covered by OSHA.

22
The guidelines identify four general elements critical to the

development of a successful safety and health management

system:

■ Management leadership and employee involvement.

■ Worksite analysis.

■ Hazard prevention and control.

■ Safety and health training.

The guidelines recommend specific actions, under each of these

general elements, to achieve an effective safety and health

program. The Federal Register notice is available online at

www.osha.gov. 

State programs

The Occupational Safety and Health Act of 1970 (OSH Act)

encourages states to develop and operate their own job safety and

health plans. OSHA approves and monitors these plans. There are

currently 26 state plans: 23 cover both private and public (state and

local government) employment; 3 states, Connecticut, New Jersey,

and New York, cover the public sector only. States and territories

with their own OSHA-approved occupational safety and health

plans must adopt standards identical to, or at least as effective as,

the federal standards. 

OSHA consultation services

Consultation assistance is available on request to employers

who want help in establishing and maintaining a safe and healthful

workplace. Largely funded by OSHA, the service is provided at no

cost to the employer. Primarily developed for smaller employers

with more hazardous operations, the consultation service is

delivered by state governments employing professional safety and

health consultants. Comprehensive assistance includes an appraisal

of all-mechanical systems, work practices, and occupational safety

and health hazards of the workplace and all aspects of the

employer’s present job safety and health program. In addition, the

service offers assistance to employers in developing and imple23


menting an effective safety and health program. No penalties are

proposed or citations issued for hazards identified by the consultant. OSHA provides consultation assistance to the employer with

the assurance that his or her name and firm and any information

about the workplace will not be routinely reported to OSHA

enforcement staff.

Under the consultation program, certain exemplary employers

may request participation in OSHA’s Safety and Health

Achievement Recognition Program (SHARP). Eligibility for participation in SHARP includes receiving a comprehensive consultation

visit, demonstrating exemplary achievements in workplace safety

and health by abating all identified hazards, and developing an

excellent safety and health program.

Employers accepted into SHARP may receive an exemption from

programmed inspections (not complaint or accident investigation

inspections) for one year. For more information concerning consultation assistance, call 800-321-OSHA or visit www.osha.gov.

The OSHA Voluntary Protection Program (VPP)

Voluntary Protection Programs and onsite consultation

services, when coupled with an effective enforcement program,

expand worker protection to help meet the goals of the OSH Act.

The three levels of VPP, Star, Merit, and Demonstration, are

designed to recognize outstanding achievements by companies

that have successfully incorporated comprehensive safety and

health programs into their total management system. The VPP

motivates others to achieve excellent safety and health results and

establish a cooperative relationship between employers,

employees, and OSHA.

For additional information on VPP and how to apply, contact the

OSHA regional offices listed at the end of this publication or call

800-321-OSHA or visit www.osha.gov.

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Strategic Partnership Programs

OSHA’s Strategic Partnership Program, the newest member of

OSHA’s cooperative programs, helps encourage, assist, and

recognize the efforts of partners to eliminate serious workplace

hazards and achieve a high level of worker safety and health.

Whereas OSHA’s Consultation Program and VPP entail one-on-one

relationships between OSHA and individual work sites, most

strategic partnerships seek to have a broader impact by building

cooperative relationships with groups of employers and employees.

These partnerships are voluntary, cooperative relationships

between OSHA, employers, employee representatives, and others

(e.g., trade unions, trade and professional associations, universities,

and other government agencies). 

For more information on this and other cooperative programs,

contact your nearest OSHA office, call 800-321-OSHA, or visit

www.osha.gov.

The OSHA Alliance Program

Alliances enable organizations committed to workplace safety and

health to collaborate with OSHA to prevent injuries and illnesses in

the workplace. OSHA and its allies work together to reach out to,

educate, and lead the nation’s employers and their employees in

improving and advancing workplace safety and health. 

Alliances are open to all, including trade or professional organizations, businesses, labor organizations, educational institutions, and

government agencies. In some cases, organizations may be

building on existing relationships with OSHA through other cooperative programs. 

There are few formal program requirements for alliances, which

are less structured than other cooperative agreements, and the

agreements do not include an enforcement component. However,

OSHA and the participating organizations must define, implement,

and meet a set of short- and long-term goals that fall into three categories: training and education; outreach and communication; and

promotion of the national dialogue on workplace safety and health. 

25


OSHA training and education

OSHA area offices offer a variety of information services, such as

compliance assistance, technical advice, publications, audiovisual

aids and speakers for special engagements. OSHA’s Training

Institute in Des Plaines, IL, provides basic and advanced courses in

safety and health for federal and state compliance officers, state

consultants, federal agency personnel, and private sector

employers, employees, and their representatives.

The OSHA Training Institute also has established OSHA Training

Institute Education Centers to address the increased demand for its

courses from the private sector and from other federal agencies.

These centers are nonprofit colleges, universities, and other organizations that have been selected after a competition for participation

in the program.

OSHA also provides funds to nonprofit organizations, through

grants, to conduct workplace training and education in subjects

where OSHA believes there is a lack of workplace training. Grants

are awarded annually. Grant recipients are expected to contribute

20 percent of the total grant cost.

For more information on grants, training, and education, contact

the OSHA Training Institute, Office of Training and Education, 1555

Times Drive, Des Plaines, IL 60018, (847) 297-4810. For further information on any OSHA program, contact your nearest OSHA office.

Information available electronically

OSHA has a variety of materials and tools available on its

website at www.osha.gov. These include e-Tools such as Expert

Advisors, Electronic Compliance Assistance Tools (e-cats), Technical

Links; regulations, directives, publications; videos, and other information for employers and employees. OSHA’s software programs

and compliance assistance tools walk you through challenging

safety and health issues and common problems to find the best

solutions for your workplace.

26


OSHA publications

OSHA has an extensive publications program. For a listing of

free or sales items, visit OSHA’s website at www.osha.gov or

contact the OSHA Publications Office, U.S. Department of Labor,

200 Constitution Avenue NW, N-3101, Washington, DC 20210.

Telephone (202) 693-1888 or fax to (202) 693-2498. 

Contacting OSHA

To report an emergency, file a complaint, or seek OSHA advice,

assistance, or products, call (800) 321-OSHA or contact the nearest

OSHA regional or area office listed at the end of this publication.

The teletypewriter (TTY) number is (877) 889-5627.

You can also file a complaint online and obtain more information

on OSHA federal and state programs by visiting OSHA’s website at

www.osha.gov.

For more information on grants, training, and education, contact

the OSHA Training Institute, Office of Training and Education, 1555

Times Drive, Des Plaines, IL 60018, (847) 297-4810, or see Outreach

on OSHA’s website at www.osha.gov.

27


Region I

(CT,* ME, MA, NH, RI, VT*)

Boston, MA 02203

(617) 565-9860

Region II

(NJ,* NY,* PR,* VI*)

201 Varick Street, Room 670

New York, NY 10014

(212) 337-2378

Region III

(DE, DC, MD,* PA,* VA,* WV)

The Curtis Center

170 S. Independence Mall West

Suite 740 West

Philadelphia, PA 19106-3309

(215) 861-4900

Region IV 

(AL, FL, GA, KY,* MS, NC,* SC,*

TN*)

Atlanta Federal Center

61 Forsyth Street SW, Room 6T50

Atlanta, GA 30303

(404) 562-2300

Region V

(IL, IN,* MI,* MN,* OH, WI)

230 South Dearborn Street, 

Room 3244

Chicago, IL 60604

(312) 353-2220

Region VI

(AR, LA, NM,* OK, TX)

525 Griffin Street, Room 602

Dallas, TX 75202

(214) 767-4731 or 4736 x224

Region VII

(IA,* KS, MO, NE)

City Center Square

1100 Main Street, Suite 800

Kansas City, MO 64105

(816) 426-5861

Region VIII

(CO, MT, ND, SD, UT,* WY*)

1999 Broadway, Suite 1690

PO Box 46550

Denver, CO 80202-5716

(303) 844-1600

Region IX

(American Samoa, AZ,* CA,* HI,

NV,* Northern Mariana Islands)

71 Stevenson Street, Room 420

San Francisco, CA 94105

(415) 975-4310

Region X

(AK,* ID, OR,* WA*)

1111 Third Avenue, Suite 715

Seattle, WA 98101-3212

(206) 553-5930

28

*These states and territories operate their own OSHA-approved job safety and

health programs (Connecticut, New Jersey, and New York plans cover public

employees only). States with approved programs must have a standard that is

identical to, or at least as effective as, the federal standard.

Note: To get contact information for OSHA Area Offices, OSHA-approved state plans,

and OSHA Consultation Projects, please visit us online at www.osha.gov or call us at

(800) 321-OSHA.

OSHA Regional Offices