Fresh Look at Diesel Exhaust Smoke Removal

Ted Siska

Editor’s note: This article represents the opinion of the author, not the opinion of Fire Apparatus & Emergency Equipment.

This article attempts to provide an overview of practical, available, Clean-Air-compliant technology that can be used to reduce particulate emissions from new or older diesel-powered apparatus as new trucks and ambulances replace older pieces in the fleet, for the ultimate purpose of reducing firefighters’ exposure to diesel emissions on the job.

Firefighters, emergency medical technicians (EMTs), staff, and neighbors of fire stations can experience adverse health effects from unfiltered diesel exhaust smoke exposure. Recent advances in diesel fuel, engines, and air sampling technology prompt a fresh look at diesel exhaust smoke in the emergency service.

There’s no set formula for diesel exhaust smoke, a byproduct of combustion. Engine smoke from one truck is never the same as the exhaust smoke from another. Diesel smoke from any diesel-powered equipment is always a pervasive air contaminant. Twenty years ago, the International Agency for Research on Cancer classified diesel exhaust a “probable human carcinogen.” In April 1995, the Health Effects Diesel Working Group warned that diesel emissions have the potential to cause adverse health effects including pulmonary and cardiovascular disease and cancer.

Neither the Occupational Safety and Health Administration (OSHA) nor the National Fire Protection Association (NFPA) has published permissible exposure limit standards for whole diesel exhaust smoke. The 1990 National Institute for Occupational Safety and Health (NIOSH) study “Exploratory Assessment of the Risk of Lung Cancer Associated with Exposure to Diesel Exhaust Based on a Study of Rats” found excess risk at the upper range of diesel particulate exposure. NIOSH merely recommends that workers’ exposure be reduced to the “lowest feasible concentration.” Diesel smoke contains varying amounts of chemicals known to be carcinogenic and lethal, including arsenic, benzene, formaldehyde, nickel, and a host of polycyclic aromatic hydrocarbons.

The United States Environmental Protection Agency (EPA) set the reference concentration, used as a health benchmark for chronic noncarcinogenic health effects, such as cough; flu-like symptoms; headache; nausea; and asthma, for whole diesel exhaust, which includes diesel particulate and the complete mixture of chemical content. The EPA reference concentration for diesel smoke is five micrograms per cubic meter of air.

Noxious chemicals in diesel smoke function by binding to the surface of microscopic soot emitted from exhaust tailpipes and stacks and disperse rapidly through the ambient atmosphere. Unique properties of diesel smoke are that ultrafine particulate matter may be present even though invisible to the eye and that it has an extremely long airborne residency.

History of Use

Diesel propulsion has a relatively short history in the fire service. First appearing after World War II, early diesel fire trucks were noisy, oily, smelly, and smoked like chimneys. Diesel engines in fire apparatus grew increasingly more popular beginning in the 1970s. Today, almost all new fire trucks and a majority of medium-duty ambulances are diesel-driven.

When fire trucks had gasoline motors, fire department personnel generally performed their own engine maintenance in-house. Many firehouses installed drop-hose systems where a manually attached exhaust hose connected the tailpipe to a powered ventilator fan piercing through the roof or sidewall. Although engine repair at the fire station is a thing of the past, drop hose remains the most common method of combating workplace contamination from engine emissions.

With advantages over gasoline that include greater efficiency, leaner burn, and lower flammability, diesel engines are now the first choice for buses, tractors, stationary machinery, construction equipment, mining machinery, and over-the-road heavy duty trucks. Concerns about atmospheric pollution, urban smog, acid rain, and global warming drove legislated changes in both fuel and engine technology that affect every fire department and ambulance corps.

Changes from 2007

Since 2007, diesel fuel, a fractional distillate of petroleum, has been refined to achieve lower sulfur content to reduce formation of sulfuric acid from the exhaust. Ultra-low-sulfur fuel (ULSF) is now available everywhere in the United States and Canada.

On January 1, 2007, Highway Diesel Rule EPA07 went into effect, through which the EPA imposed more strict emissions reduction regulations than before. Diesel engine manufacturers met the directives by designing higher efficiency exhaust gas recirculation, much higher combustion temperatures, and adding diesel particulate filters (DPFs) or oxidizers into their engines. Urban diesels, such as garbage trucks, school buses, and fire apparatus, do not run long enough at high speed to achieve sufficient exhaust temperature to ignite diesel exhaust and require autoregeneration to cleanse the DPF. This is done by injecting a mist of fuel into the exhaust stream, chemical additives, propane flame, and/or electric heating coils.

Technological advances during the past five years force responsible officials to reevaluate the best available technology. As fleets are upgraded to newer engines, cleaner-burning diesel fuel combusted at much higher temperatures presents radically different emissions problems for fire departments.

NFPA Requirements

Every truck built specifically for the fire service since January 1, 2009, is manufactured to NFPA 1901, Standard for Automotive Fire Apparatus (2009 ed.). Chapter 12 of the standard covers chassis and vehicle components and requires that the “exhaust temperature shall not exceed 851°F measured at the exhaust pipe when the unit is in regeneration.”

Not every truck used by the fire service is necessarily built to NFPA 1901. This would include Class 4 (e.g., Ford F450, Dodge Ram 4500, and GMC 4500) and Class 5 (e.g., International MXT, Ford F550, Ram 5500, and GMC 5500) vehicles as well as new bare chassis remounts. General duty trucks are built to Truck Manufacturers Association standards and EPA07 Standards, which presents a possible tailpipe exit temperature of 1,200°F during the autoregenerative cycle.

To lessen the chance of a passerby being burned by the intense heat, several manufacturers (Ford, Freightliner, General Motors, International, and Pierce, for example) incorporate clever, sometimes elaborate, tailpipe tip diffusers to cool and deflect exhaust blast to the pavement. The deflectors present a problem when it comes to attaching a nozzle for exhaust extraction. Hose manufacturers have adapters to fit the new tailpipe configurations, which don’t modify or interfere with the original exhaust system design. EPA07 News Bulletin January 11, 2008, discusses modifying an EPA07-compliant vehicle’s tailpipe design.

Indoor contamination of the workplace with soot particulate too small to be seen with the naked eye that has extremely long airborne residency occurs when an apparatus enters and leaves the building, blowing exhaust back inside. No pollution emits from the tailpipe after the vehicle is parked and the engine is shut down to allow hose attachment. Note that exhaust hose manufacturers recommend that the hose be connected to the apparatus before it backs in.

Diesel Exhaust Studies

Manual attachment of a hose nozzle to a tailpipe four times hotter than boiling water poses increased direct exposure for those assigned to attach it, according to a 2000 study of 40 sites by British Occupational Hygiene Society. Its research, “Survey of Exposure to Diesel Engine Exhaust Emissions in the Workplace,” published in the Oxford Journal, states, “Generally, personal exposures will be expected to be higher than background exposures since the operator will usually be closer to the source of the pollutant.” According to the study, the ratio of personal to background concentration is 1.5 for respirable dust, 1.6 for organic carbon, and 1.6 for total carbon.

Few studies have ever been made of firefighters’ exposure to diesel smoke. The February 2011 NIOSH Firefighter Fatality & Prevention Report, “Controlling Diesel Exhaust Exposure Inside Firehouses,” states, “Industrial hygiene principles suggest that tailpipe capture devices would be the most effective way to reduce firefighters’ exposure to occupational diesel exhaust.” Seven years before, the July 2004 study, “Diesel Emissions in Fire Stations” by the Resource Information Center for Health, Technology, and Environmental Recovery (RICHTER) Foundation, says, “The most efficient and cost-effective way to reduce emissions is to install active diesel particulate filters with oxidation catalyst in all diesel trucks and equipment used in fire station. Other filters can be installed providing they will not interfere with particulate matter (PM) filter and oxidation catalyst.”

Previously published American scientific occupational air sampling studies involved diesel exhaust inside underground mines (C. Todradze, Encyclopedia of Occupational Health and Safety, Geneva Labour Office, 1983; Roger & Hancock, Coal Miners Exposed to Diesel Exhaust Emissions, 1980; Baurngard, Estimation of Diesel Particulate Matter in Underground Mines, 1986), and inside garages (Gamble, Jones, Mishall, Epidemiological-Environmental Study of Diesel Bus Garage Workers, 1987).

For the very first time it has ever been done, the Oregon Occupational Safety and Health Division, using methods and procedures endorsed by the Mine Safety and Health Administration, and equipped with the latest improved scientific air sampling equipment-that enabled collection of respirable carbon dust on a silver membrane filter for 97 percent accuracy and collection of nitrous oxide, nitrous dioxide, and sulfur dioxide-conducted a complete first-hand, real-time exposure study of real-life firefighters throughout their daily routines on November 10, 2009, and April 29, 2010 (OR-OSHA Consultative Services reports #09-01224, 10-01194, 10-01195, 10-01196, and 10-01197).

Oregon OSHA Study

The Oregon OSHA scientific sampling studies, completed by industrial hygiene consultant Russ Reasoner, were taken on the job at four different fire stations in the Portland, Oregon, area. They reveal previously unknown and surprising facts about firefighters’ daily exposure to diesel smoke. Air samples were collected inside bays and living quarters, outdoors in proximity to those stations, traveling to and from the stations to emergency scenes, and at the scenes. All known previous diesel exhaust smoke studies were limited to sampling inside buildings or confined spaces.

Although 23 tests may not seem like a lot, the Oregon OSHA study actually involved a higher number of tests than most air sampling studies referenced in Department of Health and Human Services (HHS) National Toxicology Program 2011 12th edition “Report on Carcinogenic Diesel Exhaust Particulate.” The 23 tests performed in Oregon represent sampling at four different buildings ranging in age from 10 to 30 years old and housing 15 pieces of diesel apparatus of various makes including pumpers, ladder trucks, tankers, and hazmat trucks. Of those, two were 2009 or newer (NFPA 1901), and none of the rest were more than ten years old.

From his findings, which allowed a two-times higher set reference concentration than the EPA, Reasoner concluded that traditional building-mounted ventilation and exhaust hose extraction systems “do not provide firefighters with relief from diesel exhaust exposure.” His tests found diesel particulate concentration at unsafe levels inside the firehouse; on the apron outside for apparatus checks, which also raised levels inside if the doors were open; and at the scene, especially when a cluster of trucks had their engines running.

According to the study, “Four out of 23 tests, or 17 percent of the tests, indicated a high risk of firefighter exposure to diesel exhaust as an average diesel exhaust exposure ranging from 1.5 to 3.5 times above the EPA small particulate air standard of 50 micrograms per cubic meter in a 24-hour day. The firefighter tasks involved with these exposures were mostly limited to working between units while idling. Specific tasks were related to apron work and EMS compartment activity between running units. These exposures were categorized as average firefighter exposure to diesel exhaust where their exposure time is expected to approximate the sample time period and to be moderate to high frequency (one or more times per 24 hours). The four tests that showed direct readings above the standard were related to outside apron or field activity between units. None of the four high-risk exposures were related to ‘tap-out’ activity.”

Note that working between running apparatus that are idling at an incident is unavoidable. Apparatus that are on the apron are typically not left running. But, bay doors are often left open in fair weather, allowing exhaust to enter the building in the so-called canyon effect.

The study continues, “Five out of 23 tests, or 22 percent of the tests, indicate moderate risk of firefighter exposure to diesel exhaust as a maximum exposure ranging 2.2 to 5.0 times above the EPA small particulates air standard of 50 micrograms per cubic meter in a 24-hour day. The firefighter tasks related to these exposures were mostly inside bay activity or about idling units on the apron and the station doors open …. The living space for Station 5 was sampled for diesel particulate. Direct readings indicate firefighters active in the living space may be exposed to diesel particulate 16 times above the EPA standard.”

Oregon OSHA recommendations said “One clear outcome from the sample tests is that a fire station-mounted ventilation or exhaust capture system will not provide firefighters relief from exhaust exposure when active in the field, especially when between idling units. Unfortunately, the highest risk of exposure to diesel exhaust is the firefighter activity in between idling units.” And, “If technologically feasible, install on the units aftermarket diesel exhaust devices that can reduce diesel exhaust particulate at or below the EPA standard. This will ensure the firefighters out in the field, where there is highest risk to diesel exhaust exposure, will be protected. In addition, the same level of protection will be provided for station activity, aprons, and tap-outs.”

Onboard Emissions Control

Those recommendations are indeed technologically feasible using aftermarket onboard diesel emissions control retrofit systems. Because fire apparatus is tuned for maximum acceleration for short runs more than for fuel economy, intermittent exhaust filtration offers the best of both worlds: unfettered horsepower for racing to the emergency scene and smoke reduction at select places-indoors, on the apron, and at the scene.

Aftermarket exhaust systems are, for the benefit of the public, regulated by federal and state law. Not all commercially available systems may be legally installed on fire apparatus and ambulances. Every project, procurement, contract, or grant funded wholly or in part by any United States government agency, including the military, DHS, FEMA, and GSA, must be in compliance with the federal Clean Air Act by Executive Order 11738 signed by President Nixon September 10, 1973.

Section 203(a) of the Clean Air Act 42 U.S.C. 7522(a)(3) prohibits the removal, interference, or bypassing of any emissions control device, muffler, oxidizer, or other element of the manufacturer’s stock design installed on any motor vehicle or engine. The EPA Office of Mobile Source Enforcement Memorandum 1A, several subsequent clarifications and policy interpretations, and EPA Exhaust System Repair Guidelines establish strict standards for manufacturers of aftermarket exhaust systems and persons who perform normal maintenance and repair or undertake modifications or alterations. Those rules require that aftermarket diesel emissions control filters and systems be either EPA-verified or exempt by virtue of California Air Resources Board (CARB) Aftermarket Parts Division Executive Order.

The only vehicles on which noncompliant parts may be legally installed are race cars; show cars never driven on the street; and military tactical vehicles such as tanks, mobile artillery pieces, and amphibious assault vehicles. Some aftermarket parts suppliers claim to meet OSHA, NIOSH, and NFPA standards for diesel smoke, which simply do not exist. But, unless those suppliers have EPA verification or a CARB Executive Order, their parts are not legal to buy or install on any fire truck, ambulance, or other emergency vehicle.

Over the past decade, major improvements have been made in engine design and diesel fuel, resulting in lower power output but substantial reduction in emissions and some fuel savings, while presenting fresh challenges to maintaining a safe workplace environment, a fundamental liberty interest, at the same time.

TED SISKA is president of Smoke Blotter, Inc. He invented and holds patent on the Phantom Switch RF proximity control diesel emissions system. He is a professional engineer educated at the University of Notre Dame and has been employed as senior engineer at Monsanto Chemical, Lockheed Martin, and Hadco Electronics. He has taught classes in mathematics, facilities management, and forensic contracting.

More Fire Apparatus Current Issue Articles
More Fire Apparatus Archives Issue Articles

No posts to display