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Changes to Intrinsically Safe Standard Can Affect Your Radio Coverage

When the National Public Safety Telecommunications Council (NPSTC) learned a new version of the intrinsically safe (IS) standard affecting land mobile radio (LMR) was to be introduced by January 1, 2012, they created a working group to tackle a resulting problem: The new standard would have a serious negative technical and financial impact on public-safety users.

The impact of the changes to the standard will extend far beyond basic product-design considerations on portable radio equipment. Significant system infrastructure expansion might be necessary to maintain current geographic and in-building coverage, regardless of the fact that funds and additional FCC channels/spectrum necessary to support such expansion are probably not available.

The Problem

To meet the new standard, the power of radios must be reduced. Handset power is a critical parameter in the design of radios systems to cover an agency’s jurisdictional responsibility. The typical portable radios used by public safety range from two to six watts, varying by frequency band. A decrease of as little as 3 dB (50%) in the transmit power of a portable radio will cause a coverage reduction of almost 20%.

On the fireground, firefighters often use simplex communications (radio to radio), and a power level of one to two watts on the fireground won’t work well. Power reduction will limit the range in the talk-around mode; in-building coverage will also be adversely impacted, creating safety issues.

Further, the power reduction resulting from compliance with the new requirements in the revised standard could be more severe, resulting in an even more devastating reduction in radio coverage and requiring significant additional tower sites at added costs to compensate for the coverage loss.

Possible Solutions

NPSTC’s Intrinsically Safe Radio Working Group approached the International Society of Automation, Underwriters Laboratories (UL) and FM Approvals to ask them to provide an extension to the effective date of the new standard; this will allow sufficient time to develop a new standard specifically for LMRs or modify the 60079 standards (UL and FM versions).

The change to the new standard, FM 3610:2010, appears to be driven by the desire to harmonize the standards with international standards and not by a concern that requirements in the existing FM 3610:1988 standard are unsafe. Several different paths at developing a new standard or modifying the existing standard are currently in progress.

The majority of the 60079 standard is acceptable to the LMR industry. The major concern is a safety-factor increase from FM 3610 standards to the new 60079 standard.

NPSTC met with OSHA in April and reviewed its concerns with the new standard for IS equipment:

  • The new standard will require major infrastructure improvements—new transmission and repeater towers to be constructed in addition to land acquisition to construct new towers. Engineering analysis indicates implementation of many of the requirements in the new standard will result in a 3db to 10db reduction in transmitter power.
  • The new standard will require modification to battery packs to attain IS compliance. This will require larger batteries to retain full shift operating time for first responders. Any size and weight increases are a major concern to first responders who already carry heavy equipment.
  • Reduced transmission power may prevent first responders from communicating when in a building to request assistance or additional support—transmission may not be strong enough to reach high floors or basement levels through concrete and steel.

Noting that OSHA doesn’t have the authority to modify a consensus standard, NPSTC requested that OSHA retain FM 3610:1988 as an appropriate test standard for LMRs until a new or modified standard that addresses both safety and performance aspects of the radio is published. NPSTC also asked OSHA to recognize that the Telecommunications Industry Association and the LMR industry are developing a new standard for consideration under their program.

OSHA representatives said they may consider extending the recognition of FM 3610:1988 as an “appropriate test standard” beyond the proposed withdrawal date. However, this would only be possible under special circumstances with sufficient justification (e.g., no other comparable standard exists or the new standard presents a technical deficiency when compared to the existing standard).

Subject-matter experts from industry have been asked to translate the technical issues into general language to describe the safety effects the new standard will have on the actual user. OSHA plans to move on the issue in summer or early fall.

Reduced power is a safety issue because communications will be less reliable. Putting in more sites to accommodate the reduced power is not necessarily an answer to that problem as there isn’t enough spectrum to do that.

FM has said that public safety can continue to operate under the 1988 standard until 2016, which seems to be a weakness in their argument that this equipment is unsafe. Manufacturers can still manufacture batteries under the old standard as long as there are no changes.

Marilyn Ward is executive director of the National Public Safety Telecommunications Council.

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