Dirty diving

     The arena of public safety diving is as vast and challenging as the dive operations that teams perform. Dive units across the nation do not operate under one national recognized standard or set of rules. And as such, they face unique obstacles specific to themselves and their jurisdiction. But even with a lack of standardization, all divers can perform demanding and challenging operations safely, thanks to new technological breakthroughs in equipment design and development.

     The National Incident Management System, or NIMS, classifies a public safety dive team as a law enforcement unit equipped and trained to perform a variety of location and recovery operations, as well as provide safety divers for special events. With this in mind, scientists, designers and manufacturers needed to create equipment that allows for safety, comfort and versatility. In addition, equipment had to be developed that would protect the diver from contact with pollutants and contaminants, and is also cost effective for teams operating on limited budgets.

What lies below

     Most public safety dive teams are chartered to perform all or some of the three specific types of diving operations: Body recovery, vehicle recovery and evidence recovery. Each of these presents specific contaminant concerns as well as challenges not found in sport diving. Vehicles in the water often leak gasoline, battery acid, brake fluid, transmission fluids and oils which can easily burn divers' skin or create other complications if absorbed into the skin or ingested via a regulator that dangles from the mouth.

     Body recoveries are probably the most challenging concern for public safety units for several reasons. Bodies begin to deteriorate at a high rate after life is extinguished. The decaying victim leaches bodily fluids, including urine, feces, gastric juices, cerebra-spinal fluid and others into the surrounding water. In addition, the high concentration of contaminants provides a breeding ground for bacteria and viruses to grow and infest.

Suiting up

     Diving manufacturers began analyzing the needs of public safety teams and looked at ways to mitigate exposure to such contaminants. Advances in exposure systems, respiratory and air delivery units, and even the ability to add underwater communications were developed. Thus the standard dress for public safety divers was born.

     Wetsuits, by their name, are designed to trap a thin layer of water between the suit fabric and the skin. The body temperature of the diver heats the water, which in turn keeps the diver warm.

     However, due to the contaminants present in most public safety dives, wetsuits quickly became taboo. The wetsuit's design issues in contaminants and traps them next to the diver's skin, thus allowing some contaminants to be absorbed into the body.

     Dive equipment manufacturers and agencies sought to correct this design flaw by introducing a newer and safer exposure suit, which is referred to as a dry suit. Dry suits are designed to completely encapsulate the diver and prevent water from entering by using special latex seals around the wrist and neck. In addition, the attached dry gloves and dry hoods kept water away from the majority of the body, with the exception of the face.

     Dry suits were initially made from neoprene rubber. However, neoprene, while keeping water out, would still absorb contaminants on the external fabric layer. A diver could be exposed simply by removing the suit after a particularly nasty dive. Alternative suit materials and designs were invented to minimize this risk and also to make the suit more comfortable. Dry suits made from bi-laminate, tri-laminate and polyurethane were developed, but each had its limitations when operating in certain contaminants like gas and oil.

     Designers like Dick Long, with Divers Unlimited International, and companies like Hunter Gates and Trelleborg Viking, began developing suits made from vulcanized rubber. Further, each of these companies began performing permeation tests to determine how long suits could perform surrounded by certain chemicals and hazards.

     Trelleborg Viking recently created an additional dry suit design, referred to as the Haz-Mat Diving System, to minimize exposure and maximize safety. The HDS suit is made from a newer material called NITEC that boasts a more durable fabric than other suit types, and longer permeation times. Trelleborg also added specially designed inlet and exhaust valves that have double seals to keep leaks from entering the suit.

Inhalation and ingestion

     Protecting divers from inhaling airborne particles or ingesting droplets of contaminated water is another concern when constructing dive equipment. Standard regulators that use a mouthpiece violate the exposure protection protocols necessary to dive safely in contaminated waters. These regulators are often removed and replaced from the mouth, and often come in contact with the water while diving.

     Imagine a diver performing a body recovery and surfacing to ask for a tool or body bag. The diver would have to remove the regulator from his mouth, which would then hang down, potentially coming in contact with the water. When the diver replaces the regulator mouthpiece and takes a breath he would inevitably aspirate small droplets of water. These drops of water could contain small particles of necrotic skin, bacteria and viruses from the deceased.

     To better protect divers, designers began developing special full face mask designs. When used with a dry suit, full face masks completely surround the diver's face and keep the water from coming in contact with the diver's skin and respiratory tract. Full face mask designs have improved through the years, and the implementation of silicone skirts, positive pressure and balanced air delivery regulators have vastly improved on the safety and comfort of previous designs. The Interspiro Divator MKII is a prime example; this mask has rapidly been adopted as the industry standard for public safety, commercial and military dive units.

     An added benefit of full face masks is the addition of underwater communication devices. Full face masks can be outfitted with either wireless or hardwired systems that allow divers to talk to one another underwater and communicate directly with surface support personnel. This single addition drastically improved safety via direct communications between all parties. In addition, dives can be better directed, dive times shortened and exposure times limited.

More useful diving tools

     Other specialized equipment like side scan sonar systems, remotely operated vehicles with underwater camera systems, magnetometers and surface-supplied air delivery systems have increased the overall effectiveness and abilities of these dedicated professionals.

     Side scan sonar systems were originally designed for military and scientific diving communities. However, as technology has advanced prices have dropped dramatically and placed these units in the hands of divers worldwide. Side scan sonar units are either mounted to the hull of a vessel or towed behind the boat. The device transmits sound waves beneath the boat and reads the response. Images are displayed on either a computer screen or a paper printout with exceptional clarity. The newer sonar systems are even capable of reading the raised lettering on radial tires at depths exceeding 30 feet. The utilization of this single device allows divers to pinpoint a target before entering the water, and minimizes the in-water time necessary to perform complicated and dangerous search patterns.

     Remotely operated vehicles are unmanned submarine units that house simple to complex navigation and camera equipment. The units are connected to the surface via a tether or wire, and are controlled by a joystick or keyboard command device. The ROV's camera system transmits video back to a topside control system and allows users to view underwater images through a monitor or television. Teams can conduct a search for evidence, vehicles and bodies without endangering the lives of divers.

     Underwater magnetometers are old fashioned tools that have come into the new age of affordability and portability. J.W Fishers and other companies produce low cost but effective systems that can detect metal objects underwater and, sometimes, up to 20 inches beneath sediment or further. Advances in handheld units and underwater metal detectors have been readily accepted by teams and routinely deployed as standard equipment. They are cost effective and allow divers to perform sweeping searches while looking for smaller metallic objects like handguns, jewelry or shell casings.

Surface-supplied air

     Finally, surface supplied air delivery units have quickly become the standard for dive units. These systems are comprised of an approved oil-less air compressor and a series of in-line filters that scrub and clean the air. They create clean, breathable air at a pressure and flow rate capable of sustaining a diver at depth for extended periods of time. They also pump clean air to the diver's full face mask or helmet by means of a tether and umbilical system.

     Umbilicals consist of at least three but sometimes four individual components: A hose that transports the compressed air to the diver; a safety line to connect the diver to the surface; hardwired communication lines for the divers' earphones and microphone; and a device called a pneumofathometer, which allows the surface to monitor a diver's depth at all times.

     Adopting surface-supplied air into public safety diving requires advanced training and understanding of diving physics and physiology. But the system also allows for longer dive times, safer air quality, and also eliminates the gauges and loose hoses that can entangle and endanger divers. In the event of entrapment, a diver has the extended air supply while he slowly and safely frees himself.

     Public safety divers vary drastically from their sport diving counterparts. As technology continues to advance, improvements in design, material selection and functionality are sure to come, and future offerings are sure to have a direct impact on the continued safety and capabilities of these dedicated individuals.

Michael S. Glenn teaches Forensic Sciences and Underwater Diving Operations at North Carolina Justice Academy. He welcomes comments at mglenn@ncdoj.gov.