Digital Communication Systems

Conceptual and Legislated Design Considerations for
Emergency Warning Systems in Industrial Facilities
by Paul Huene

Emergency Warning Systems (EWS) are a necessary part of any industrial facility. Statistics indicate it is not a matter of “if” there will be a plant emergency, but “when.” Thus, the EWS ensures that injuries to people, damage to the environment, and to plant infrastructure is kept to a minimum. There are as many philosophies about EWS design as there are types of plants. There are fundamental considerations, however, that must be taken into account before constructing a new facility. In addition, there may be known deficiencies in the EWS in existing plants, which owners have an obligation to rectify.

Corporate Responsibility

Industronic manufactures digital voice, data and video systems for public address, alarm and safety communications.

Most industrial organizations have clearly stated Health, Safety, and Environment policies. They have an internal mandate to protect the health of workers and neighbours. They have a mandate to provide a safe working environment, and finally, they have a mandate to protect the environment from spills, discharges, and waste. It is clear that the three prongs of the HS&E policies are intricately related. They set the tone and direction, and provide some of the details required through specific sub-policies. The problem with the policies, however, is that they are often too general and fail to address the “how” and “what” to do in the event of an emergency.

We have seen over the years how acceptable standards of workplace HS&E have changed. People and the environment are protected from process discharges; they wear protective clothing and other equipment. Actions that were previously allowed are now forbidden. Safety has become a culture within organizations, generally driven from the top down, but in collaboration with front-line employees, special interest groups, and non-governmental agencies (NGOs).

Despite the improvements we have made, there is room to get better. The U.S. Chemical Safety & Hazard Investigation Board, investigating a 2006 fire and explosion in a plant which produced polyvinyl chloride (PVC), found that during a release of vinyl chloride monomer (VCM), workers failed to perform per the requirements of the Emergency Response Plan (ERP). Five workers were killed, three were injured and the surrounding community was evacuated for two days. VCM is both flammable and carcinogenic. While there were conflicting instructions within the ERP, workers failed to evacuate the area, failed to don protective breathing apparatus, and failed to activate emergency alarms. There was no automated mechanism to notify neighbours. The facility had not had a large release training exercise in over 10 years.

The Board recommended that the company “clearly characterize emergency scenarios, address responsibilities and duties of responders, describe evacuation procedures, and ensure adequate training.” The cause of the accident is listed as human error. The plant has not been rebuilt.

In 1989, an explosion and fire killed 23 and injured 314 in a U.S. petrochemical plant. Debris was scattered over a six mile radius. The U.S. Fire Administration & National Fire Data Center investigation showed that human error during maintenance was the cause. In total there were about ten explosions over the duration of the crisis. There was no gas detection or audible alarm system in place in the area where the gas leak and explosion took place. Employees were not familiar with emergency evacuation procedures, yet had only 60 – 90 seconds to make life and death decisions. The lack of functional EWS in the affected area resulted in a “run for your life” response from workers.

The investigators further found that incoming telephone calls jammed the phone lines and delayed broadcasts on the EWS. Emergency personnel were tied up with the media and dealing with the public, rather than doing their jobs. Investigators also found that emergency personnel had incomplete information to broadcast. It is estimated the explosion caused approximately $1.5 billion in damage and lost production. The company was fined $4 million.

Legislated Requirements for Emergency Warning Systems

Provincial
Provincial legislation is generally covered through the Occupational Health and Safety Act. In Alberta, this falls under the auspices of the Department of Human Resources and Employment. Some pertinent points from the Act are included here:

• Building an Effective Health & Safety Management System
  • Identify the types of disasters and emergencies
  • Assess the potential for harm
  • Develop procedures to deal with each type of emergency
  • Train workers to deal with each type of emergency
  • Install warning systems such as fire alarms
  • Install emergency equipment including emergency communication systems
  • Practise

Federal
Federal legislation is covered through Human Resources and Social Development Canada, and the Canada Occupational Health and Safety Regulations Part 10 – Hazardous Substances:

• Where reasonably practicable, the employer shall provide automated warning and detection systems where the seriousness of any exposure to a hazardous substance so requires

International
The National Fire Protection Association (NFPA) takes things a little further. In its Annex E Mass Notification Systems, its states:

• “NFPA 72 contains requirements that can impact the application of mass notification systems. Coordination of the functions of a mass notification system with those of a fire alarm system is essential in order to provide effective communication in an emergency situation. Conflicting or competing signals or messages from different systems could be very confusing to occupants and have a negative impact on the intended occupant response. Where independent systems are used, the mass notification system would need to interface with the fire alarm system to effect related control actions such as temporary silencing of notification appliances. The use of a single integrated combination system might offer both economic and technical advantages. In any case, coordination between system functions is essential.”
• “For the purposes of this annex, a mass notification system is considered to be a system used to provide information and instructions to people in a building, area, site, or other space using intelligible voice communications and possibly including visible signals, text, graphics, tactile, or other communications methods.”

• All employees and contractors on site should know what each alarm means and what the required response is, if the cause of the alarm has the potential to affect them.
• The design of the alarm system should prevent masking and flooding of alarms. Masking is where one alarm noise masks a similar sounding alarm, preventing the operator from detecting the signal. Flooding happens when a system alarms which has a ‘knock on’ effect on other related systems, the result of which is the triggering of myriad other alarms, flooding the site with sound.
• There should be a noticeable difference between alarm sounds used to alert, rather than for routine communication and information signals.

• Consider using verbal auditory warnings in combination with visual warnings. Use of both methods has been found to improve compliance with the warning message.

• An employer must have and maintain an employee alarm system. The employee alarm system must use a distinctive signal for each purpose.
• The employee alarm system shall provide warning for necessary emergency action as called for in the emergency action plan.
• The employee alarm shall be distinctive and recognizable as a signal to evacuate the work area or to perform actions designated under the emergency action plan.
• The employer shall assure that all employee alarm systems are maintained in operating condition except when undergoing repairs or maintenance.

Conceptual Design Considerations for Emergency Warning Systems

Each facility requires a different type of emergency warning system in order to address the various types of emergencies and responses required. As indicated by the legislative requirements outlined above, a single-tone air horn is inadequate to provide proper notification to personnel in most circumstances. Radios are often considered to meet the requirements for emergency warning systems, but in fact, they have many limitations. These include dead batteries, contractors and visitors not being issued with radios, coverage limitations due to large metal structures and enclosures, high ambient noise levels, lack of security from eavesdroppers and terrorists, system-wide failure due to “keyed” microphones, and a lack of disciplined communication during an emergency.

Multi-tone generators add some flexibility during emergencies, but as stated earlier, confusion can be created if the tones are similar to one another. The problems are three-fold. The first is identifying what the tone means, and secondly, what the correct response is. Finally, how are personnel notified if the required response is non-standard? The problems are accentuated for new hires and visitors who may not have a complete knowledge of how to respond to the tones.

Various coloured strobe lights help, but have many of the same limitations as the multi-tone generators.

So what does a good emergency warning system consist of? Following the recommendations of NFPA 72 Annex E, the system should be designed by a person specifically trained in such design and implementation. It must meet the requirements of the legislation of the jurisdiction having authority. It must meet the intentions of the corporate HS&E policy, as well as industry standards and good engineering practices.

It is recommended that the fire alarm system be integrated into the emergency warning system. The emergency warning system should consist of a library of speech messages, with specific messages output according to the specific input device(s). In unusual (unforeseen) circumstances, emergency personnel should be able to provide special instructions by overriding the automatic functions of the emergency warning system. A pre-tone should be broadcast prior to the speech instructions. This provides a “heads up” that there is an emergency, and that detailed instructions are about to be given. Personnel can then think about what they are to do, and act accordingly, based on a full understanding of the message. Activation of strobe lights will enhance the pre-tone warning. During an emergency, it is imperative that communication between emergency personnel and others be disciplined. In order that instructions be clearly understood, only one party can speak at a time. It is up to emergency service personnel to determine who can speak and when. The emergency warning system must accommodate this function.

From a technical standpoint, the emergency warning system should be completely self-monitoring. This functionality is critical to ensure that the system works when it is required to work. The EWS can actually become a liability if it does not work as expected during a crisis situation. Manual monthly tests are also required, with activation by different devices on consecutive tests. This ensures that even if the self-monitoring function fails, other component failures will be found. All components should be monitored, including input and output cards, amplifiers, power supplies, wiring, speaker coils, activation devices and appliances, as well as intercom and call stations. Maintenance reports should be self-generating to ensure that repairs are made in a timely fashion. These reports should be automatically directed to emergency services personnel, to the maintenance department, or to the organization contracted to provide repair services. Logs should also be generated to show that failures have been repaired.

System layout in a plant environment requires the experience of trained field technicians and engineers. In an existing plant, sound level surveys should be completed, and speaker placement determined. Many factors must be taken into account for speech messages to be heard and understood. First, the message should be broadcast at 10 to 15 dB above the ambient noise level. Speakers should be placed near noise sources, as the sound will attenuate at the same rate as the noise. The system should allow for varying output levels based on the ambient noise level. For example, during maintenance shutdowns it is desirable to reduce the overall output, as long as it remains 10 to 15 dB above ambient. It may also be desirable to reduce the output at night, to avoid having a negative affect on neighbours. Speakers must be of a type and placed in a way to limit or eliminate reverberation (echo). This ensures that the message will not be garbled. The presence of large structures such as buildings, vessels, and so on may create an acoustical shadow. Within the shadow, the message will be at a lower sound level, and may not be heard or understood. It can also happen that messages from different speaker arrays may arrive at a location at slightly different times. Depending on the time differential and the sound intensity, the message may be unintelligible. Weather effects such as wind speed, direction, temperature, and humidity levels can also have a negative influence on sound level quality and level.

Conclusion

The design and implementation of an Emergency Warning System or Mass Notification System requires a thoughtful process to determine what the potential emergencies are, and what should be done in the event that they occur. The system should be flexible and robust. It is important to work closely with the equipment manufacturer to ensure that the product will meet plant requirements now and in the future. The system should be designed in such a way that it can accommodate changes in its technology, changes within the plant environment, and changes in legislation. Such a system may not have the lowest price, but provides the best long term value, and ensures that emergency warnings are heard, understood, and acted upon in a way that preserves life, protects infrastructure, and the environment.

For additional information or to to discuss your project call, fax or e-mail us.