Emergency Air Monitoring: Beyond the Plume

By Brian Ladds

During the summer of 1999, a large fire at an oil recycling facility affected a large area within the city of Calgary and resulted in extensive evacuations. It was many hours into the incident response before any sophisticated air monitoring was available to incident command. A post-fire review identified a need for this detection capability in the southern Alberta region. Afterward, a unique partnership developed between the Calgary Fire Department and the Provincial Alberta Environment office to produce an air-monitoring vehicle (AMV) that would en-hance public safety at major fires and chemical releases.

The identification of airborne chemical components in a smoke plume, combined with atmospheric data gathered on-site in real time, can help the incident commander (IC) determine when and where the plume will extend, what possible concentrations to expect, and whether to shelter in place or evacuate the community. The decision to evacuate or shelter in place carries an immense liability in terms of financial and life safety issues that must be precisely managed—not approximated.

Since late September 2002, the Calgary Fire Department Hazardous Materials Division has operated its AMV at a variety of building/structure fires. Using a host of onboard analytical sensors, we have been able to provide a fairly detailed analysis of the smoke composition from these fires. This information enables the IC to establish an exclusion zone around the fire building. This will certainly benefit firefighters’ and other emergency scene personnel’s long-term health and safety as well as provide the public with increased protection from the hidden dangers associated with the products of combustion.

OPERATING MECHANICS

An ambient air stream is continuously drawn through a sample tube positioned above the roof of the vehicle into a glass manifold mounted inside, where the instruments each have an individual sample line. A discrete pump draws the air sample from the manifold, through the detector, and then exhausts the stream to the exterior of the vehicle, eliminating contamination to the interior workspace. A fan at the bottom of the sample manifold improves instrument response by providing sufficient airflow through the main intake stream. Future upgrades will include grab sample introduction to the sensor array.

The ambient instrumentation package consists of sensors for sulphur dioxide (SO2), hydrogen sulphide (H2S) and other total reduced sulphur compounds (TRS), nitrogen oxide (NO), nitrogen dioxide (NO2), other oxides of nitrogen (NOx), and a chlorine (Cl2) analyzer. An onboard dust or suspended particulate analyzer scans, classifies, and quantifies the incoming air stream into three sizes of particle groups: 10 microns (PM-10), 2.5 microns (PM-2.5), and 1.0 microns (PM-1.0). A heater in the sample tube removes moisture that would otherwise cause particle classification errors.

A Fourier Transform Infrared (FTIR) ambient air analyzer continuously scans the incoming air sample, then produces and displays an absorbance spectrum about every 10 seconds. A computer compares the ambient spectrum against a set of reference spectra of more common chemical compounds. This unit operates at a spectral resolution of 0.5cm-1 (wave numbers) and provides extensive detail of the chemical compounds present in the smoke plume. Liquid nitrogen cools the detector, improving resolution of dilute compounds among the background noise.

A portable infrared air analyzer allows us to sample the air from inside a structure or a location into which we cannot drive the AMV. This unit does not have the spectral resolution of the FTIR but still provides a fairly good determination of the most abundant chemical compounds in the air sample.

An onboard weather station provides temperature, atmospheric pressure, relative humidity, and wind speed and direction. In addition, a portable weather station can be deployed at the scene to send wireless data back to the truck with a range of about 5 km distance. This information is fed directly into a computer that runs a sophisticated plume modeling program. Incident command can be immediately updated regarding where the plume will progress, with predicted concentrations and expected time of arrival, thus providing for improved evacuation coordination.


(1) The AMV monitors an ARFF training exercise. (Photos courtesy of author.)
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Support equipment includes a combination printer/scanner/fax/photo card reader, a digital cell phone, and an analog cell phone with a high gain antenna that provides good coverage in remote areas. Electrical power is provided by a self-contained 7-kw electrical generator integrated with the vehicle’s fuel supply and uses an exhaust scrubber to reduce possible contamination of the air sample.

The vehicle itself was limited to a Ford E-450 chassis with a custom cube. A larger unit would have reduced the ride quality and subjected the instruments to undue vibration and shock. The interior space includes two work stations, a cascade breathing air system with hoses and SCBA escape packs for the operators, as well as the capability to pressurize the interior cab to maintain a clean environment inside while sitting in the plume.

Maintaining a positive pressure inside keeps out contaminants (tested and confirmed) and increases operator comfort by eliminating cumbersome airlines and harnesses. Comforts include heat and air-conditioning systems for respective climates.

At the time of writing, the Calgary Fire Department, Alberta En-vironment, and Calgary Health Region are studying the most suitable set of standards and guidelines for exposure—what standard to adopt when determining how acutely toxic the smoke really is. For the purposes of firefighter and emergency personnel exposure guidelines, we have adopted the threshold limit values (TLVs) published by the American Conference of Government Industrial Hygienists Inc. (ACGIH), as these tend to be the lowest among the most popular groupings of exposure guidelines. So far, no one particular set of standards adequately covers the firefighter short-term exposure limits while addressing the needs of the general public.

OBSERVATIONS

Several significant patterns have emerged from the data that could have a significant impact on firefighting and other emergency services personnel working a fire scene. Aside from the obvious visible smoke and the associated respiratory hazards, there are substantial quantities of fine invisible suspended particulate released from the plume.

Airborne suspended particulate 10 microns in size are called PM-10 and generally result from grinding operations, windblown dust, and vehicles driving on roadways. Particles less than 2.5 microns are termed PM-2.5 and are the result of combustion and other airborne pollutants such as SO2, NOx, and VOC interacting. Air quality index guidelines for PM-10 classify 255-354 µg/m3 (micrograms—1 millionth of a gram—per cubic meter of air) as unhealthy for the elderly, children, and persons with existing respiratory conditions.1 Air-borne particulate units are µg/m3.

Our measurements indicate that being underneath a smoke plume without respiratory protection is extremely dangerous. Most smoke plumes have peaked at 2,000-2,500 µg/m3 for PM-10 and PM-2.5. The maximum dust analyzer reading is 6,500 µg/m3, and we have recorded a structure fire in a motel of ordinary construction where the PM-10 and PM-2.5 were off the scale for several periods of five minutes and more. We have recorded extremely high levels of fine suspended particulate up to 30 m each side of a smoke plume with a steady 5-10km/h wind. We have observed an elevated smoke plume that dropped its particulate several kms away, yet the smoke visually appeared to be carried farther on the wind before dispersing.

To date, the structure fires we have attended have been of ordinary construction such as a motel, multistory residential dwellings, and light industrial occupancies. Aside from the expected carbon dioxide, carbon monoxide; oxides of nitrogen and sulphur; and compounds such as benzyl chloride, ethyl benzene, ethylene, formaldehyde, hexane, hydrogen chloride, hydrogen sulphide, methane, methanol, methyl chloride, pyridine, styrene, toluene, and xylenes have appeared frequently in the smoke plumes in significant concentrations.


(2) The haz-mat officer (left) monitors the instrumentation while the haz-mat coordinator (right) operates the plume modeling software.
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(3) The AMV at a multiresidential occupancy fire.
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EMERGING ASPECTS

Recently the AMV has been requested to assist arson investigators though the application of portable equipment. After-the-fire customer service includes ensuring the air quality inside a structure is suitable for occupation and cleanup activity.

Emergency worker safety is paramount to our ethical, moral, and administrative responsibility to understand in detail the environment firefighters are exposed to and how to best protect them. Correlation of the long-term health effects to identified chemical exposures and comparison with baseline heavy metal blood work during regular examinations will help benefit firefighters. It is our hope that this detection ability will help prevent both acute and chronic respiratory conditions or other induced injury to responders who must work under these adverse conditions and to the public at large.


(4) The AMV has numerous applications during and after the fire, and its data are being used to study the environment to which firefighting personnel are exposed in an effort to protect them.
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The Calgary Fire Department is registered to ISO-14001; thus, the department has a responsibility to protect the environment. Firefighting operations and techniques have an impact on the byproducts of combustion and the associated runoff. A better understanding of the potential contamination is fundamental to the actions necessary for an effective cleanup.

After the oil recycling fire in 1999, the City of Calgary services spent more than a month washing homes, gardens, streets, parks, and in some cases the entire inside of some homes and businesses. Monitoring the contaminated air is no longer a matter of acquiring information that is “nice to know” but rather a liability and risk-avoidance requirement. n

Endnote

1. U.S. EPA Guidelines for Reporting of Daily Air Quality Index, July 1999, EPA-454/R-99-010.

Brian Ladds is a hazardous materials officer and in his fifth year with the Calgary Fire Department in Alberta, Canada. He has a bachelor’s degree in chemistry, a diploma in engineering, and seven years of experience as an industrial chemist and safety officer. His training includes NFPA 472 Technician and CBRN live agent training and response.

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