Chemical Monitors: No All-in-One Solution Yet

Each day, more than half a million shipments of hazardous chemicals rumble down America's roads and rails. Many of them are toxic industrial chemicals, or TICs. Responders who are aware of these shipments realize that they are only a crash, derailment, or leak away from a release that could injure or kill hundreds or even thousands.

Until 9/11, responders knew how to react to releases of TICs or other dangerous chemicals. They looked first for the large, brightly colored Dept. of Transportation (DOT) hazard labels carried on all chemical shipments. Red warns if a chemical is flammable. Yellow is for oxidizers, orange for explosives, and white for inhalation hazards.

The DOT label gave responders an initial heads up about the danger they faced. For more detailed information, they could consult shipping and handling labels, four-digit chemical identifiers and shipping manifests. Expert advice was usually only a phone call away.

Derailed
That changed on 9/11. It raised the specter of chemical terrorism. Attention quickly focused on nerve, blood, blister and mustard chemical warfare agents (CWAs). Yet CWAs are hard to acquire and use. Japan's Aum Shinrikyo, for example, failed several times before its 1995 sarin nerve agent attack that killed 12 on the Tokyo subway.

More unnerving, TICs could be used as weapons. Like CWAs, TICs are deadly. Some, like chlorine and phosgene, were used as poison gas in World War I. Equally important, TICs are readily available. Terrorists could blow up a toxic chemical plant and hope for a wind to blow it towards residential areas. More frighteningly, they could hijack a tanktruck or derail a train of TICs as they crisscross our suburbs and cities.

Terrorists will not proclaim the nature of their attack. If they purloin a tanktruck, they will strip off its TIC labels and throw out its manifest. The first responders on the scene may not even realize they are under attack. Unless they can accurately read the signs and symptoms of the victims, they may not realize TICs or CWAs are present.

The only way to truly identify the specific threat is to test. Without accurate tests, responders cannot assess risk. Nor can they select the right protective equipment, establish the hot zone perimeter or treat victims medically.

Yet despite the proliferation of new, more portable and more powerful technologies, getting the information they need is no easy matter.

Detecting Issues
In part, this is because CWAs and TICs are not easy to detect. Most chemical monitors involve an inherent tradeoff. Those that take readings from a distance are not very good at identifying specific threats. To achieve greater accuracy, responders must use technologies that require them to walk into the hot zone and take air and liquid samples.

Even then, finding the toxin is not easy. "You show up at an incident and there are millions of chemicals floating around," says Bruce Quimby, a chemist at Agilent Technologies Inc., which develops analytical equipment used in chemical laboratories.

"You might have burning wood, diesel fuel, tires, all sorts of stuff," he continues. "The weapon you're looking for is small and hiding under all those other chemicals. You have to sort through them to identify the toxic materials. And remember, a lot of the stuff in smoke is toxic too."

It is not easy for a detector to separate one chemical from another. In order to sort through this chemical stew, portable devices are usually sensitized to find only a handful of the most widely used chemical agents. Otherwise they are likely to set off false alarms. "Even then," says Quimby, "it's terribly difficult to get an accurate reading."

Agilent's solution is a gas chromatograph-mass spectrometer, an instrument used to identify unknown chemicals in laboratories around the world. Unfortunately, it costs more than $100,000 and weighs about 150 pounds. It has a place in a portable laboratory (something even most large cities lack), but no one will carry it into the field.

Concerns
More portable technologies present a mixed bag. While most are fairly simple to use, they require responders to take samples from near or inside the hot zone itself. They are not always reliable. Nor can they pick out CWAs or TICs from air or liquid samples unless they are first tuned to find those specific chemicals, so responders have to know what they are looking for before they find it.

Moreover, nearly all methods have real limitations. Since the late 1990s, the U.S. Army Soldier and Biological Chemical Command (SBCCOM) has been testing commercial CWA chemical detectors (see Sidebar, Additional Resources for Responders, for a Website containing the report). It found plenty of reasons for concern:

• Some detectors were easily contaminated during laboratory testing. They would require far more frequent cleaning and recalibration during a field use.
• High humidity or cold weather degraded the ability of many units to detect CWAs. It caused others to fail entirely.
• Some units responded to one type of CWA but not another.
• One unit's display proved unreadable, and its batteries ran down during use.
• Many units raised false alarms. In fact, one detector gave false positives up to 65 percent of the time when used around engine exhausts, smoke and other vapors.
• At least one unit proved too inconsistent for field use.

The Best Detector
Given SBCCOM's thorough testing, it is easy to become discouraged. Yet detection technology is advancing rapidly. Driven by both government R&D funding and the promise of more sales to securityconscious departments, vendors are making their instruments smaller, faster and more powerful than before. Professional organizations are discussing new standards that will guarantee minimum performance standards and make it easier to compare models.

Even the most powerful detector is not likely to replace the responder's first line of defense: his or her own eyes.

"The signs and symptoms point us toward the piece of monitoring equipment to use," says Oakland, Calif., Fire Dept. hazmat specialist Dan Keenan.

Each type of TIC or CWA has its own unique signs and symptoms, he explains. Nerve agents, for example, cause pinpoint pupils (miosis), salivation and convulsions. Blood agents cause convulsions but pupils remain normal size. Chlorine causes mild eye, nose and throat irritation, nausea, and frothy secretions after several hours.

Keenan's urban search & rescue (USR)/hazmat team carries an array of monitors and sensors at all times. If they see something unusual people convulsing on the ground or dazed and wandering they will assess the symptoms to determine what monitor to use.

Fire Dept. of New York Chief Joseph Pfiefer agrees. "We look at identification as concentric circles, from the least to most sophisticated analysis," he explains. "You could give people all sorts of gadgets, but they'll still need training and continuing education to make the right judgement. We don't depend on equipment alone, but make judgements based on our observations."

Gadgets
Responders will always count on their observations to determine how to proceed. Yet they must also rely on gadgets to identify the specific threat they face.

Most fire crews carry at least one chemical sensor, a multigas monitor. These units generally measure concentrations of oxygen, carbon monoxide, combustible gases and hydrogen sulfide (a foul-smelling chemical added to natural gas to alert users of potential leaks). Responders use them to investigate gas leaks and strange odors, appraise safety during confined space rescue, and determine carbon monoxide levels during overhaul.

Multigas monitors could provide more capabilities than that. Custom models can measure a variety of TICs, including chlorine, phosphine and hydrogen cyanide. At $600 to $2,000 (depending on functions and features), they are also reasonably priced. The problem, of course, is that they can detect only a handful of chemicals. They might make sense for responders near facilities that use or ship those TICs. They are unlikely to help responders who cannot pinpoint their most likely threats.

Colorimetric tubes can detect a much broader range of gaseous threats. Developed in the 1930s, these small tubes change color when exposed to low concentrations of CWAs or TICs. Each tube measures a specific CWA or TIC threat, and there are more than 100 different tubes.

Colorimetric Tubes
Oakland's Keenan wears a set of colorimetric tubes on his belt. "We carry them for choking, blister, nerve and other chemical agents," he says. "They show results in parts per million concentrations. You break off the end of the tube and suck air through them to see if they change colors."

It takes Keenan about 50 pumps, or 4 or 5 minutes, to get a reading. This is because each tube is really a small laboratory, explains Draeger Safety Inc. gas detection product manager Craig Rogers. As the pump draws air through the tube, it collects a sample large enough to test. It then carries out one or more chemical reactions to see if the sample will cause a color change. This takes a few more minutes.

Vendors have sought to simplify the process. Draeger, for example, sells kits originally developed for NATO that can detect five CWAs at once. Responders can activate the tubes before entering the hot zone, and manipulate them while wearing Level A suits. Draeger also supplies electric pumps to eliminate manual pumping. Colorimetric tubes are relatively inexpensive. Individual tubes start at around $10. Draeger's five-tube CWA set costs $189, though it must be thrown away after one use.

Unfortunately, tubes have two key weaknesses. First, responders have to read victim symptoms accurately enough to know which tubes to use. Then they have to walk into the hot zone to take the reading.

Other technologies, particularly electronic sensors, enable responders to take readings from further away. They also have their own unique set of strengths and limitations.

Electronic Detectors
Photo ionization detectors, ion mobility sensors and surface acoustic wave sensors are the most widely used portable electronic gas detectors. All work by zapping molecules with a jolt of energy, then measuring their behavior afterwards.

Ion mobility spectrometry (IMS) sensors, for example, usually jolt samples with Beta radioactivity. This gives any CWAs or TICs in the sample an electrical charge, turning them into ions. The ions are drawn towards an electrical field at the end of a drift tube. IMS recognizes different chemicals by clocking their travel time and the strength of their charge when they reach the end of the tube.

IMS does a very good job of identifying CWAs. Oakland FD, for example, uses an APD 2000 IMS from Environmental Technologies Group Inc. "It can actually read nerve, blister and riot control agents such as pepper spray and mace," Keenan says. "First responder versions cost $2-10,000, and that's within reach."

The problem with IMS units is that they require a library of chemical profiles to compare their readings with benchmark results. For responders to load the right library, they must already know the agents for which they are looking.

Photo ionization detectors (PIDs) use ultraviolet (UV) light sources to ionize molecules. They then measure the voltage of all the ions in the sample to determine the concentration of the agent.

The problem with PIDs, says Draeger's Rogers, is that they measure the concentration of volatiles at a scene but do not differentiate between one volatile and another. Nerve gas, diesel exhaust, and volatiles from burning plastic all look the same. "It may give you a number, but you can't tell everything that's there," says Rogers. SBCCOM tests have shown that PID UV sources are vulnerable to fogging when used in high humidity.

Yet PID has its uses, says Mine Safety Appliances Co. (MSA) group product manager Len Blatnica. PIDs can measure trace amounts of volatiles, which make them useful in establishing a perimeter. Individual units can be small enough about the size of a cell phone to carry anywhere, and they are very simple to use.

MSA and other suppliers can include them in multigas meters. This adds roughly a $500-1,000 premium to the cost of a unit. The result is a product that warns responders if they encounter high levels of unknown chemicals.

Surface acoustic wave (SAW) detectors absorb suspect chemical agents onto a series of polymer films. This changes the mass of the films. When they vibrate at high speed, the change in mass alters their resonant frequency. The SAW then compares the new frequency with a library of CWA and TIC frequencies to find a match.

Oakland's SAWs, for example, are tuned for nerve and blister agents. Because they are so sensitive, they generate lots of false positives, says Keenan. He's learned to live with it. "If you're using it, it's because you're seeing symptoms and something has happened," he says. "We would use this with colorimetric tubes to get a real positive reading."

Shopping List
Most responders seem to be combining different chemical detectors to achieve an accurate reading. There are many more technologies that could be used. These range from flame photometry, infrared spectroscopy and photoacoustic infrared spectroscopy (PIRS) to filter-based infrared spectrometry, electrochemistry, sensor array technology and flame ionization.

Some of these technologies are incorporated in CWA detection kits used by the military. Others are being reconfigured in innovative ways. Several vendors now sell units that combine more than one sensing technology. Others are seeking to develop portable versions of laboratory instruments. MSA has created a system that links PIDs into a wireless network that can be deployed to provide alarms at rock concerts, football games and other major events.

Many responders have their own shopping lists. Three months after 9/11, the RAND Science and Technology Policy Institute surveyed responders at a conference. Their responses and those of others like them are guiding today's research. Among the most wanted technologies:

• Passive, fast-acting badges that responders can wear on garments to warn of unseen dangers.
• High-sensitivity sensors that can detect small amounts of CWAs and TICs at a distance.
• Fast, simple test kits and devices similar to those used to identify illegal drugs.
• Comprehensive monitors that detect and identify threats from a wide range of chemicals.
• Chemical sensors inside buildings that would act like fire alarms to warn responders of threats before they reached the scene.

By voicing their requirements, responders are helping to push the technology forward. Even before 9/11, portable sensors were growing smaller, smarter, faster, more reliable and better able to detect a threat at a distance. Since then, Department of Homeland Security and other government agencies have pumped additional millions into research that will make future devices even better.

Yet all monitoring systems even those still on the drawing board have weaknesses as well as strengths. It may take a decade or more before comprehensive solutions emerge that are portable, fast, easy to use, and capable of remote identification of all potential CWAs and TICs.

Until then, responders must find ways to get the most out of today's limited technologies. That often means combining technologies to ensure an accurate assessment.

In the end, though, the first line of defense remains responder knowledge. Someone must assess the situation. He or she must read the signs and symptoms of victims. And then have the courage to walk into the hot zone and to get the sample.