When Communicating Saves Lives
Systems should have high intrinsic safety ratings to ensure safe and effective communications depite the type and / or level of the emergency.
- By Rolf Eberl
- Aug 01, 2008
Good communication is one of the most important
tools for ensuring workers’ safety
and work efficiency, especially when confronting
the hazards of confined space entry.
Benefits are also realized in productivity, costs, and
workers’ confidence. In some circumstances, communication
makes an otherwise impossible task possible.
OSHA defines a confined space as any space that has
limited or restricted means of entry or exit, is large
enough for an employee to enter and perform assigned
work, and is not designed for continuous occupancy by
the employee. These areas include, but are not limited
to, underground vaults, tanks, storage bins, vessels, pits
or sumps, and silos. This definition is also consistent
with that of the National Fire Protection Association’s
1670, Standard on Operations and Training for Technical
Rescue Incidents, 1999 Ed.
Choosing Communications
It’s not always a simple task to choose a communication
solution that will satisfy OSHA or other mandatory or
discretionary requirements to provide effective communications
in all situations and still be readily accepted
by employees. Entrants are often encumbered with
equipment, such as self-contained breathing apparatus
(SCBA), personal alert and gas detection devices, and
safety harness apparatus.
Firefighting is dangerous enough; poor communications
in confined space entry can be fatal. Therefore,
communication systems utilized should have high intrinsic
safety ratings so as to ensure safe and effective
communications despite the type and/or level of the
emergency. This means greater worker safety and reduced
employer liability.
In examining the conventional means of communications
used, you’ll find that many of these have limited
application and usefulness. For example, direct voice
transmission (talking or shouting), works only in low-noise
environments and over relatively short distances.
Loud hailers can extend the distance to some degree but
may be cumbersome and limited when more than one
entrant is involved. Hand signals work in line-of-sight
applications and require constant visual contact between
communicants.As soon as a back is turned, a vital
hand signal will not be seen.Tugging rope will signal the
recipient only if the rope is not snagged and conveys
only the very basics of intelligence.
Electronic communications, which offer better solutions,
fall into two main categories: “wireless” and
“hard-line.”
Wireless Communications
Wireless communication devices transmit signals
through the air, usually via radio frequency waves (i.e.,
two-way radio), providing unhampered mobility to the
user. For this reason, it becomes the system of choice for many applications. Radio equipment has its own shortcomings,
however, making its use limited or even unacceptable
in many confined space applications. New solutions
may use infrared to link users, but these have
other limitations without “line of sight.”
Without line of sight, communications may become
erratic or, worse, entirely missing. Steel, concrete, or
brick surrounding (or in proximity to) the radio can
have a shielding effect.Additional antenna elements installed
in strategic locations may alleviate these problems,
but this becomes expensive and impractical in
portable or emergency applications.
A duplex system has each radio operating on two
frequencies simultaneously. In this case, transmit and
receive frequencies are open all of the time in both directions.
Keying the radio to transmit is not necessary
because the transmitter is on all of the time. This
method meets OSHA requirements for continuous
communication but can use a lot of power and is limited.
This is an important factor because most systems are
battery operated and should be investigated before making
a communication system choice.
If more than two radios are required, it becomes
necessary to use an additional repeater to accommodate
duplex operation.PTT (push-to-talk) or VOX (voice actuated)
switches used to switch the radios to transmit
are less acceptable because they prevent continuous
communications.
Potentially volatile explosive atmospheres will require
the use of intrinsically safe equipment.Assembling
a multi-radio, intrinsically safe duplex system is an attractive
solution only if cost is not a consideration.
In summary, although popular for other applications,
wireless communications should not necessarily
be the system of choice for confined space communications.
Hard-line Communications
In tethered or hard-wired systems,wires are used to interconnect
headsets and components to form an intercom
between the workers. Advantages of this system
outweigh the disadvantages of a physical interconnection
between components.Initial and operating cost are
low, and non-line-of-sight communications are guaranteed.
Full duplex lets everyone talk at once and ensures
no messages are missed. PTT or VOX controls are
not required, allowing hands-free operation.
Wired communications can typically be used by as
many as 10 people.Most systems have immunity from
RFI (radio frequency interference), which can be encountered
from nearby equipment that generates RF,
such as arc welders, computers,fluorescent lighting, etc.
Wired communications typically do not generate their
own RF and do not cause interference to nearby electronics
and other sensitive equipment.
In the event that a confined space rescue becomes
necessary, most wired intercom systems can provide the
privacy needed to prevent monitoring or interference by
those not involved with the operation.
Recently the American Society for Testing and Materials
(ASTM) recommended, in summary, that systems:
(1) be intrinsically safe; (2) have continuous,
hands-free voice communications; (3) be dedicated and
private; (4) not affect readings of other equipment (such
as gas detectors); (5) if battery operated,have a low-battery
warning or back-up power; (6) accommodate a
minimum of three users; (7) allow for communications
among all entrants, as well as the attendant; (8) must
work in conjunction with any personal protective
equipment used; and (9) must be impervious to the
chemicals within the space.
Communication Ropes
Even though training and research into hard-line systems
may not be new, communication ropes are quite
unique. By incorporating communication wires directly
into safety ropes, you reduce equipment, improving
workers’ efficiency and safety.When considering the
benefits of communication rope, make sure it is high
performance and meets OSHA’s requirements, provides
a means of rescuing entrants from a confined space,and
eliminates the need for addition cable.
The Benefits of Intrinsically Safe Equipment
In confined space or rescue situations, poor communications
and substandard systems can be fatal. It is highly
recommended that you choose a product or system
with the highest intrinsic safety rating so that workers,
employees, and employers are guaranteed the correct
communication components are being used, no matter
what the emergency. This provides not only the
greatest worker safety, but also liability protection for
the employer.
References
1. Occupational Safety and Health Administration (OSHA) 29
CFR 1910.146.
2. American Society for Testing and Materials (ASTM) Designation:
F 1764-97.
This article originally appeared in the August 2008 issue of Occupational Health & Safety.