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The purpose of the Fire Mechanics Section is to promote standardization of fire apparatus and equipment preventative maintenance, improve safety standards and practices, promote workshops, conferences, and seminars related to the purposes of this Section, and to promote cost savings through standardization of building and equipment purchasing and maintenance.

RECENT FIRE MECHANIC NEWS

Posted: Apr 4, 2017

Siren Limitation Training

By Chris Daly

Overestimating the effective range of a siren is a common cause of fire apparatus crashes.

Studies have shown that the effective range of a siren at a 90-degree intersection is often less than 80 feet. This effective range may be less, depending on the design of the intersection and the soundproofing properties of an approaching vehicle.

While siren limitations are a common cause of emergency vehicle intersection crashes, few emergency vehicle operators course (EVOC) programs address the topic. The goal of this article is to provide training ideas that will help demonstrate the limited effective range of a siren.

1 A class 2 sound level meter. (Photos by author.)
1 A class 2 sound level meter. (Photos by author.)

Overview

A vehicle driving on a road will have a substantial amount of noise inside the passenger compartment of the vehicle. This noise is known as “ambient noise.” Ambient noise will depend on several factors, including the noise from the engine, the radio, the HVAC system, and the friction of the tires rolling on the road surface. The ambient noise inside a passenger vehicle traveling 45 miles per hour (mph) usually averages around 65 decibels (dB).

For a siren to be effectively heard by a civilian driver, it must penetrate the body of the vehicle and become louder than the ambient noise. Studies have shown that the siren level must rise approximately 10 dB above the ambient noise to effectively break the driver’s concentration. If the ambient noise inside the civilian vehicle is 65 dB, the siren must rise to 75 dB.

The structure of a modern vehicle is designed to keep sound OUT. On average, a modern vehicle will block approximately 30-40 decibels of noise from penetrating the passenger compartment of the vehicle. This is known as “insertion loss.” If a civilian driver requires 75 decibels of siren noise to react, the siren must arrive outside the driver’s window at approximately 110 decibels, assuming an average insertion loss of 35 dB.

2 A sound level meter calibrator
2 A sound level meter calibrator.

The Problem

Most sirens are rated at around 124 dB when measured 10 feet in front of the siren. As the distance from the siren doubles, the sound pressure of the siren will drop by approximately 6 dB. This concept is known as the “inverse square law.”

It is important to understand that this 6-dB drop in sound pressure level assumes that the distance measured is directly in front of the siren. When sound pressure measurements are taken at a 90-degree angle from the siren, the 6-dB drop can be more significant. Studies have shown that the reduction in sound pressure level at a 90-degree intersection could be as high as 11 dB. This is an important teaching point, as intersection crashes occur when the fire apparatus and civilian vehicle are approaching each other at a 90-degree angle.

3 The dBA/dBC setting on a sound level meter.
3 The dBA/dBC setting on a sound level meter.

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Posted: Apr 4, 2017

Siren Limitation Training

By Chris Daly

Overestimating the effective range of a siren is a common cause of fire apparatus crashes.

Studies have shown that the effective range of a siren at a 90-degree intersection is often less than 80 feet. This effective range may be less, depending on the design of the intersection and the soundproofing properties of an approaching vehicle.

While siren limitations are a common cause of emergency vehicle intersection crashes, few emergency vehicle operators course (EVOC) programs address the topic. The goal of this article is to provide training ideas that will help demonstrate the limited effective range of a siren.

1 A class 2 sound level meter. (Photos by author.)
1 A class 2 sound level meter. (Photos by author.)

Overview

A vehicle driving on a road will have a substantial amount of noise inside the passenger compartment of the vehicle. This noise is known as “ambient noise.” Ambient noise will depend on several factors, including the noise from the engine, the radio, the HVAC system, and the friction of the tires rolling on the road surface. The ambient noise inside a passenger vehicle traveling 45 miles per hour (mph) usually averages around 65 decibels (dB).

For a siren to be effectively heard by a civilian driver, it must penetrate the body of the vehicle and become louder than the ambient noise. Studies have shown that the siren level must rise approximately 10 dB above the ambient noise to effectively break the driver’s concentration. If the ambient noise inside the civilian vehicle is 65 dB, the siren must rise to 75 dB.

The structure of a modern vehicle is designed to keep sound OUT. On average, a modern vehicle will block approximately 30-40 decibels of noise from penetrating the passenger compartment of the vehicle. This is known as “insertion loss.” If a civilian driver requires 75 decibels of siren noise to react, the siren must arrive outside the driver’s window at approximately 110 decibels, assuming an average insertion loss of 35 dB.

2 A sound level meter calibrator
2 A sound level meter calibrator.

The Problem

Most sirens are rated at around 124 dB when measured 10 feet in front of the siren. As the distance from the siren doubles, the sound pressure of the siren will drop by approximately 6 dB. This concept is known as the “inverse square law.”

It is important to understand that this 6-dB drop in sound pressure level assumes that the distance measured is directly in front of the siren. When sound pressure measurements are taken at a 90-degree angle from the siren, the 6-dB drop can be more significant. Studies have shown that the reduction in sound pressure level at a 90-degree intersection could be as high as 11 dB. This is an important teaching point, as intersection crashes occur when the fire apparatus and civilian vehicle are approaching each other at a 90-degree angle.

3 The dBA/dBC setting on a sound level meter.
3 The dBA/dBC setting on a sound level meter.

Read more

Posted: Apr 4, 2017

Siren Limitation Training

By Chris Daly

Overestimating the effective range of a siren is a common cause of fire apparatus crashes.

Studies have shown that the effective range of a siren at a 90-degree intersection is often less than 80 feet. This effective range may be less, depending on the design of the intersection and the soundproofing properties of an approaching vehicle.

While siren limitations are a common cause of emergency vehicle intersection crashes, few emergency vehicle operators course (EVOC) programs address the topic. The goal of this article is to provide training ideas that will help demonstrate the limited effective range of a siren.

1 A class 2 sound level meter. (Photos by author.)
1 A class 2 sound level meter. (Photos by author.)

Overview

A vehicle driving on a road will have a substantial amount of noise inside the passenger compartment of the vehicle. This noise is known as “ambient noise.” Ambient noise will depend on several factors, including the noise from the engine, the radio, the HVAC system, and the friction of the tires rolling on the road surface. The ambient noise inside a passenger vehicle traveling 45 miles per hour (mph) usually averages around 65 decibels (dB).

For a siren to be effectively heard by a civilian driver, it must penetrate the body of the vehicle and become louder than the ambient noise. Studies have shown that the siren level must rise approximately 10 dB above the ambient noise to effectively break the driver’s concentration. If the ambient noise inside the civilian vehicle is 65 dB, the siren must rise to 75 dB.

The structure of a modern vehicle is designed to keep sound OUT. On average, a modern vehicle will block approximately 30-40 decibels of noise from penetrating the passenger compartment of the vehicle. This is known as “insertion loss.” If a civilian driver requires 75 decibels of siren noise to react, the siren must arrive outside the driver’s window at approximately 110 decibels, assuming an average insertion loss of 35 dB.

2 A sound level meter calibrator
2 A sound level meter calibrator.

The Problem

Most sirens are rated at around 124 dB when measured 10 feet in front of the siren. As the distance from the siren doubles, the sound pressure of the siren will drop by approximately 6 dB. This concept is known as the “inverse square law.”

It is important to understand that this 6-dB drop in sound pressure level assumes that the distance measured is directly in front of the siren. When sound pressure measurements are taken at a 90-degree angle from the siren, the 6-dB drop can be more significant. Studies have shown that the reduction in sound pressure level at a 90-degree intersection could be as high as 11 dB. This is an important teaching point, as intersection crashes occur when the fire apparatus and civilian vehicle are approaching each other at a 90-degree angle.

3 The dBA/dBC setting on a sound level meter.
3 The dBA/dBC setting on a sound level meter.

Read more

Posted: Apr 4, 2017

Fire Truck of the Future

By Wesley D. Chestnut

For many years, fire trucks have been predominantly some shade of red in color with flashing lights, bells, whistles, and sirens.

At face value, it’s arguable that fire trucks haven’t changed. However, as most member companies of the Fire Apparatus Manufacturers’ Association (FAMA) can attest, these vehicles have indeed advanced technologically because of innovations; changes in standards such as National Fire Protection Association (NFPA) 1901, Standard for Automotive Fire Apparatus; or government regulations. But has anyone thought about what a fire truck might look like or be able to do in the future?

Recent Technological Advancements

Many of you can probably remember when fire trucks were equipped with mechanical engines and manual transmissions. Gauges on the pumps gave indications based on mechanical means of sensing information to provide the readout. Not too long ago, you could purchase an apparatus without antilock brakes.

Today, fire trucks are equipped with computerized engines with sophisticated after-treatment devices and automatic transmissions. Although the changes related to the engine were aided by emissions regulations set forth by the government, the use of computerized technology has brought efficiencies to the engine and the vehicle. The engine can now tell you when something is wrong with relatively accurate and specific information.

As it relates to safety of the occupants, there are two areas in which fire trucks have advanced. First, the use of advanced air bag systems to increase the protection of the occupants during a vehicle crash has been implemented in these vehicles. Second is electronic stability control (ESC), which uses computerized technology to apply the vehicle’s brakes, assist steering, and disengage the throttle to reduce the chance of a vehicle crash.

With all the technological advancements throughout the years (too many to list here), some may wonder how else the fire truck could advance. What could a fire truck of the future look like? How might it function? Below are three advancements that may be implemented in fire trucks sooner than we think.

Vehicle-to-Vehicle Communication

It might be hard to imagine a vehicle being able to communicate with another vehicle, but it is becoming a reality. If you stop to think, the engine in the fire apparatus can “talk” to the transmission. The engine can also “talk” to pump controls. So, is it impractical to think a fire truck would not be able to talk to other fire trucks or passenger cars?

Many of you may have heard of vehicle-to-vehicle communication, more commonly known as V2V. This crash avoidance technology has been reviewed by the National Highway Traffic Safety Administration (NHTSA) for more than a decade. The system relies on communication from nearby vehicles to alert drivers of potentially dangerous situations that might lead to a crash. These systems are composed of devices, installed on vehicles, which use short-range radio communication to exchange messages identifying vehicle information such as speed, direction, and braking status. The logic in these systems uses information received from other vehicles to determine if a warning is needed to alert the driver of a potential danger.

One of the concerns in motor vehicle accidents involving fire trucks is when they occur at an intersection - more specifically, when the fire truck is struck by a passenger car even after appropriate maneuvers and driver signaling. If equipped with V2V, the oncoming passenger vehicle may be able to “talk” to the fire truck and alert the driver of this big, massive piece of equipment approaching the intersection to avoid a c

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Fire Mechanics Section Board

Chair

Posted: Oct 21, 2015

Chair

Elliot Courage
North Whatcom Fire & Rescue
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Vice Chair

Posted: Oct 21, 2015

Vice Chair

Mike Smith 
Pierce County Fire District #5
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Secretary

Posted: Oct 21, 2015

Secretary

Greg Bach
South Snohomish County Fire & Rescue
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Director #1

Posted: Oct 21, 2015

Director #1

Doug Jones
South Kitsap Fire & Rescue
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Director #2

Posted: Oct 21, 2015

Director #2

Paul Spencer 
Fire Fleet Maintenance LLC
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Director #3

Posted: Oct 21, 2015

Director #3

Jim Morris
Mountain View Fire Department
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Director #4

Posted: Oct 21, 2015

Director #4

Arnie Kuchta

Clark County Fire District 6

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Director #6

Posted: Oct 21, 2015

Director #6

Brett Annear
Kitsap County Fire District 18
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Director #5

Posted: Oct 21, 2015

Director #5

Jay Jacks
Camano Island Fire & Rescue
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Legislative Representative

Posted: Oct 21, 2015

Legislative Representative

TBD
TBD
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Immediate Past Chair

Posted: Oct 20, 2015

Immediate Past Chair

Brian Fortner
Graham Fire & Rescue

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