Confined Spaces in Construction
and Atmospheric Testing
By: Dave Wagner, Global Director of Product Knowledge & iNet Product Manager,
Industrial Scientific Corporation
INTRODUCTION
In 1993, 29 CFR 1910.146 went into effect as the first federal legislation governing
entry into permit-required confined spaces in general industry. Because some
industries, such as the construction industry, were covered by specific Occupational
Safety and Health Administration (OSHA) safety regulations, they were exempt from
the confined space entry requirements of the general industry rule. The construction
standard, 29 CFR 1926, did not cover confined space entry as reflected in 2005-2009
statistics where 61% of all confined space fatalities occurred during construction,
repairing, or cleaning activities.1 As such, OSHA introduced 29 CFR 1926, Subpart
AA, the final rules governing entry into permit-required confined spaces for the
construction industry on May 4, 2015.
This paper will not define what constitutes a confined space, permit required
or otherwise, and will not attempt to determine what is and is not considered
construction, but will focus on the requirements and best practices of atmospheric
testing during confined space entry procedures.
ENTRY PROCEDURES AND ATMOSPHERIC TESTING
Atmospheric testing plays an important role in the 2015 regulation. Like the general
industry standard, the construction safety standard requires testing of the atmosphere
and verification that it is safe prior to anyone entering the confined space. Specifically
the standard states:
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Before an employee enters the space, the internal atmosphere must be tested, with a calibrated direct-reading instrument, for oxygen content, for flammable gases and vapors, and for potential toxic air contaminants, in that order. Any employee who enters the space, or that employee’s authorized representative,
must be provided an opportunity to observe the pre-entry testing required by
this paragraph.2
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Confined Spaces in Construction and Atmospheric Testing
Testing the atmosphere before an
employee enters the space means
that you must sample the atmosphere
within the space from outside the point
of entry or from some other access
point outside of the space. This testing
requires that the monitor is equipped
with a sampling pump and a sample of
the atmosphere in the space
“Testing the
is drawn to the monitor. This
atmosphere before
must be done regardless of
an employee
whether the access or entry to
enters the space
the space is vertical or horizontal
means that you
in nature. The monitor may have
must sample the
an integral pump, it may use a
atmosphere within
detachable pump, or it may use a
the space from
simple hand-aspirated pump. The
outside the point
configuration of the pump itself
of entry or from
is less important; the nature
some other access
of the confined space and the
point outside of the
confined space program should
space.”
dictate which type of pump is
best to use. If the space requires
a vertical entry or vertical access point, a
flexible sample hose with enough length
to reach the bottom of the space should
be attached to the pump. If the space
requires a horizontal entry, a rigid probe
should be attached to the pump and
used to sample the atmosphere inside
the space.
The standard requires that the
atmosphere is tested with a
“calibrated” instrument. Unfortunately,
the term “calibrated” is not otherwise
defined and there are no specific
requirements stating the frequency or
currency of the calibration. Calibration
establishes the accuracy of the gas
monitor used for testing by adjusting its
readings to a set of known standard gas
page 2 of 6
concentrations. The sensor outputs will
drift and degrade with time and will be
affected by changes in environmental
conditions and the physical condition of
the monitor. Routine calibration must be
performed to maintain accuracy of the
monitor over time. Most interpretations
of the standard agree that “calibrated”
means the gas monitor is calibrated
in accordance with manufacturer
recommendations. Calibration might
appear to be a technically difficult
operation, but most manufacturers
provide equipment to automate the
process.
As indicated in the standard above,
the order of testing is important.
Although it is most practical that all of
these potential hazards are typically
tested for simultaneously, it is the
order of recognition of the hazard
that is the key. A lack of oxygen is the
most common atmospheric hazard
encountered in a confined space and
accounts for many confined space gasrelated injuries and fatalities. For that
reason, it makes sense to verify the
oxygen concentration first. The oxygen
concentration also gives insight into the
validity of any combustible gas readings.
If the oxygen concentration is too low,
the combustible gas concentration could
be much higher than indicated, leaving
a potentially explosive atmosphere
undetected. This does not mean the
potential toxic hazards are a lesser
consideration. The order of testing
simply ensures that the most commonly
acute hazards are recognized and
mitigated first.
Under the general industry standard,
it was common to perform a pre-entry
atmospheric test, complete the permit,
and put the gas monitor away until the
next confined space entry. Recognizing
that the levels of atmospheric hazards
can change dramatically over time, or
that the work being performed in the
confined space may introduce additional
hazards, the construction standard
has much stronger language with
regard to continuously monitoring the
atmosphere.
The atmosphere within the space must
be continuously monitored unless the
entry employer can demonstrate that equipment for continuous monitoring is
not commercially available or
periodic monitoring is sufficient. If
continuous monitoring is used, the employer must ensure that the
monitoring equipment has an alarm that will notify all entrants if a specified
atmospheric threshold is achieved, or
that an employee will check the monitor
with sufficient frequency to ensure
that entrants have adequate time to
escape. If continuous monitoring is not
used, periodic monitoring is required.
All monitoring must ensure that the
continuous forced air ventilation is
preventing the accumulation of a
hazardous atmosphere. Any employee who enters the space,
or that employee’s authorized representative, must be provided with
an opportunity to observe the testing required by this paragraph.3
The equipment for continuously
monitoring the atmosphere in a
confined space is available on the
page 3 of 6
commercial market. In most cases it is
the same or similar to the equipment
used to complete the pre-entry testing.
Arguably, the best way to
accomplish continuously
“Carrying or
monitoring the atmosphere
inside the space is to remove
wearing the
the sampling pump from
monitor ensures
the pre-entry monitor, clip
that the entrants
it on the entrant, and have
are properly
the entrant carry it into the
notified by any
space. Carrying or wearing
alarm conditions.”
the monitor ensures the
entrants are properly notified
by any alarm conditions. With those
alarm thresholds properly set, the
entrants have more than adequate time
to escape if the atmosphere starts to
become hazardous. If there are multiple
entrants in the space, providing each
one with a monitor would offer the best
protection and offer the best opportunity
for the entrant to observe the testing
required by the standard.
DO’S AND DON’TS OF ATMOSPHERIC
TESTING
Every atmospheric testing program
associated with confined space entry
is filled with a number of choices that
ultimately affect the safety of workers
as they perform their daily duties.
Typically the program is far from the
core competency and productive focus
of the company performing the work.
Too often, this distraction from the
organization’s main theme causes the
program to concentrate on doing only
what is necessary to comply with
the rules rather than focus on what is
involved with the best practices in the
industry. Chapter 7 of the National Fire
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Confined Spaces in Construction and Atmospheric Testing
Protection Agency’s Guide for Safe
Confined Space Entry and Work (NFPA
350) provides best practice guidelines
for atmospheric testing in confined
space entry procedures. Following
those guidelines will help you avoid
some of the common pitfalls listed
below associated with atmospheric
testing of confined spaces.
1. Wrong sensors for the job – The
most fundamental mistake in an air
monitoring program is the lack of proper
detection equipment. Somewhere along
the way, a portable confined space
gas monitor became defined as a fourgas instrument which detects oxygen,
combustible gas, carbon monoxide and
hydrogen sulfide. While two of those
components, oxygen and combustible
gas sensors, are a must in almost
every confined space application, the
other two are not. Confined spaces
are different, and the hazards found in
them will vary. Properly assessing the
potential hazards and ensuring that
the detection equipment is capable of
effectively monitoring the hazards in
your space is essential to the success
of the program.
2. No remote sampling equipment –
Confined space entry regulations
require that the atmosphere is tested
and cleared of hazards prior to a worker
entering the space. Workers will often
lower gas monitors into a hole using
rope, which can lead to damaged
equipment and repairs that exceeds the
cost of the device.
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3. Bad zero references – It’s natural
to get to the job, turn your monitor
on, look at the readings, and initiate
a zeroing function. This is often done
without knowing whether or not the
atmosphere you are standing in at the
time is suitable for establishing a proper
zero reference on the instrument. You
must be certain that the environment
you are in is free of gas contaminants
before zeroing. A clear indicator that
you missed this step will be that the
instrument displays negative gas
concentrations in a clean atmosphere.
If your instrument is not capable
of displaying negative readings or
automatically zeros during start-up, you
likely will never know that this mistake
has been made.
4. Improper calibration – An instrument
will only be as accurate and reliable
as its calibration. The key to a good
calibration is verifying that the gas
concentration listed on the cylinder label
matches the concentration setting for
calibration in the instrument. It sounds
easy, but the instances of instrument
users picking up a cylinder of gas at one
concentration and using it to calibrate
an instrument requiring a different
calibration gas reference are too
numerous to discuss further here.
5. Failure to test the equipment before
use – The only way to be certain that
your instrument detects gas is to check
it with gas before you use it. Performing
a functional test on a gas monitor is
a simple task which takes only a few
seconds. Why would you trust your life
to a piece of equipment which you can
only assume is functioning properly?
Would you be comfortable stepping
on board an airplane if you knew that
the pilot did not perform the required
preflight inspection? Don’t skip the
preflight check on your gas monitor.
6. No correlation between oxygen and
combustible gas readings – It is often
overlooked that sensors used to detect
combustible gases in most portable
gas monitoring instruments rely on
the presence of oxygen to provide
an accurate reading. If the oxygen
concentration in an environment is
below 10%, a dangerous condition may
go undetected because the combustible
sensor will not function properly. The
best practice is to always ensure a
valid correlation between the oxygen
and combustible gas readings on your
instrument before assuming a safe
atmosphere.
7. Test it and forget it – As discussed
previously, regulations require testing
the atmosphere prior to entering a
confined space. When the testing
is complete, the instrument often
goes back in the truck. Atmospheric
conditions can change quickly and
dramatically. Because all is clear and
safe now is no indication that it will be
safe 15, 30 or 60 minutes from now. The
new regulations require continuously
monitoring the atmosphere to make
certain that it stays safe. Keep the
instrument out and continue monitoring
the atmosphere as long as the work
continues.
8. Lack of training – Workers are often
handed an instrument, assigned the
task of performing the atmospheric
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testing, and sent on the job without
any understanding of how to operate
the instrument or interpret its readings.
Training tools are plentiful. Videos,
computer-based training modules,
on-line tutorials, and personalized
seminars are all readily available
to help convey the knowledge and
competency necessary for using
gas-monitoring instruments. Don’t
go to work without having a clear
understanding of the equipment and
how to use it properly.
9. Misinterpretation of readings and
data – Many people falsely believe
that when they know a hazard exists
that they cannot identify, they can take
their portable gas monitor into the area
and it will tell them what the problem
is. Nothing could be further from the
truth. Most gas sensors are affected by
cross interferences from vapors other
than the target compound. Make sure
you understand the effects of cross
interfering gases on sensors and avoid
misinterpreting the data they provide.
10. Weak internal standards – Don’t
rely on equipment manufacturers to
set your policy standards. Equipment
manufacturers are experts on their
equipment. They are not, nor do they
claim to be in most cases, experts in
your field or operations. Make certain
that your policies are driven by best
safety practices and not by what is
most convenient or economically
feasible. Simply relying on the
“manufacturer’s recommendation” is
no way to ensure that your program
is built on the foundation of observing
best practices whenever possible.
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Confined Spaces in Construction and Atmospheric Testing
These are only a few of the common
mistakes made in air monitoring
programs throughout industry. If you
pay attention to these factors you will
be well on the way to ensuring that you
comply with the applicable rules and
that your gas monitoring program is
following the best known practices in
the field.
CONCLUSION
The new standard for confined space
entry in the construction industry
discussed above takes effect on August
3, 2015. How ready is your
Do you have the
organization to take on the
new rules? Have you defined
gas monitoring
your potential hazards? Do
equipment
you have the gas monitoring
necessary to
equipment necessary to
perform preperform pre-entry testing and
entry testing
continuous monitoring as
and continuous
required by the regulation?
monitoring as
Gas detection equipment
manufacturers such as
required by the
Industrial Scientific Corporation
regulation?
can provide a complete
solution for atmospheric
testing in confined spaces. Confined
Space Kits are available to give you all
of the equipment necessary to test
and evaluate the air within a confined
space including the gas monitor, sample
pump, sample tubing, calibration gas
and the regulator for the gas cylinder.
If your work is unpredictable and your
need for monitoring equipment is
AMERICAS
Phone: 412-788-4353
Fax: 412-788-8353
[email protected]
page 6 of 6
sporadic, there are rental programs
to help you get what you need, when
you need it, without the hassle of
owning your own set of tools. If your
confined space program is large and
maintaining your own equipment will be
an issue, there are plans available such
as Industrial Scientific’s iNet program
that will manage and maintain your fleet
while you focus on your everyday work.
If you are looking for a confined space
atmospheric monitoring solution, let the
gas detection professionals at Industrial
Scientific help you out. Visit Industrial
Scientific today at www.indsci.com or
call 1-800-DETECTS (338-3287).
Rescue Talk, (2011, November 1), Confined Space
Fatalities…a closer look at the numbers. Retrieved
from: http://www.rocorescue.com/roco-rescueblog/confined-space-fatalities-a-closer-look-at-thenumbers
1
Subpart AA – Confined Spaces in Construction,
(2015, May 4), 1926.1203 General Requirements.
Retrieved from: https://www.osha.gov/
confinedspaces/1926_subpart_aa.pdf
2, 3
ASIA PACIFIC
Phone: 65-6561-7377
Fax: 65-6561-7787
[email protected]
EMEA
Phone: +33(0)1 57 32 92 61
Fax: +33(0)1 57 32 92 67
[email protected]
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