DIVING IN CONTAMINATED WATERS: EQUIPMENT
Diving operations in contaminated waters require a great deal of equipment. Both divers and their support personnel topside must be properly equipped. While most of the equipment used topside is familiar to hazmat personnel, the diving equipment is quite different from conventional self-contained underwater breathing apparatus (SCUBA).
The diver engaged in search and rescue often must enter water with low visibility. Outfitting the diver with appropriate and properly operating equipment, therefore, is only one of the considerations—along with training, gear maintenance, and common sense—vital to planning for this type of diving. Even when everything is done correctly, however, accidents are likely due to the nature of contaminated-water diving.
Just as the levels of protectiveequipment used in haz-mat operations on land vary with each incident, so too are specific types of diving equipment best suited to specific hazards in an underwater operation. Since, however, no standards have been established for protective clothing and equipment used for diving in polluted water, selecting the most appropriate gear for a specific incident becomes even more difficult.
DIVING EQUIPMENT
From a practical standpoint, it could be said that dive teams have some criteria on which to base their choices of gear. The criteria involve the potential effects of the hazard(s) to be encountered. If, for example, contact with the anticipated contaminants would only result in mild sickness, then the dive probably could be made with only a full face mask, a dry suit, and dry gloves. This equipment probably is adequate for exposure to biological organisms commonly found in the marine environment.
In situations where the threat is from chemical or biological hazards that can produce severe illness or death, divers require a lull-coverage helmet, a dry suit, and dry gloves. A diving helmet is more difficult to remove and less prone to leaking than a full face mask. Diving with a full facemask, moreover, always presents the danger that the mask will come loose and leak underwater.
FULL FACE MASKS
The full face masks used by search and rescue dive teams are similar to those used with SCBAs for topside haz-mat incidents. They include a demand-breathing regulator and are designed to seal against the face or on a dry suit hood; the back of the head is not covered by the mask, and the mask is held in position by a head harness or “spider.”
Full face masks used for diving should be equipped with a nonreturn valve to prevent a back-flow of contaminants into the breathing system. It also should have separate inhalation and exhalation chambers to help further reduce the possibility of inhaling a spray of contaminants should leakage occur on the exhaust side of the breathing system.
Since a full face mask can leak if a strap breaks or becomes loose, another desirable feature is a positive-pressure regulator. SCUBA full face masks normally operate in the demand mode, but masks with positive pressure are designed to free flow if the face seal is broken. This very important feature can help prevent contaminants from entering the mask in the event of a leak. Positive-pressure masks also clear water automatically if the mask completely floods.
Buoyancy can be a problem with some full face masks. Masks that have a high internal volume are very buoyant, making the mask uncomfortable and the jaw fatigued. If masks meet all the other important criteria, select the one with the lowest volume.
DIVING HELMETS
Diving helmets used in search and rescue typically include a demand regulator, which makes the use of a high-pressure air supply practical, since air is not wasted by a continuous air flow into the helmet. The regulator, however, forces certain compromises. Each time the diver inhales and exhales, for example, the regulator diaphragm and helmet exhaust valves move. The movements introduce the potential for drops of contaminants to enter the breathing system. To reduce the possibility of this happening, any demand helmet used in contaminated water must have a “double exhaust system.”
The system helps to prevent water from flowing back into the helmet. The regulator and the main helmet exhausts are linked together with a special tube, and a third external exhaust valve is added to the system. Any water that manages to sneak past the outer exhaust valve is unlikely to make it past either of the two other valves. As expected, the addition of a third exhaust valve adds some breathing resistance to the helmet.
Diving helmets are quite heavy out of the water; most weigh in excess of 25 pounds. In addition, when the helmet mates to a dry suit for contaminated-water diving, divers may find it difficult or impossible to remove the helmets by themselves. For these reasons. it is not safe to use a helmet with a self-contained breathing supply only.
COMMUNICATIONS
Because of the high risks involved, communications are essential to any polluted-water diving activity. Divers must be able to call for help if needed. Almost all full face masks are designed to accept a communications system, but communications usually are clearer with a helmet than a mask.
Underwater communications may be either hard-wire or wireless. Hardwire communications systems include a topside communications box, a direct wire link to the diver, and a set of earphones and a microphone in the diver’s mask or helmet. The system also may include special waterproof connectors and splices to join all the pieces. Hard-wire communications systems provide the highest degree of reliability and clarity.
Wireless communications are another option. Although such communications are advantageous in certain situations (such as when there is a high probability of entanglement), divers should always be tethered during contaminated water dives, even when using SCUBA. The tether provides a direct line to the surface in the event the diver becomes unconscious. Since the diver must be tethered anyway, incorporating a hardwire communications line with the tether makes sense.
SURFACE-SUPPLIED AIR SYSTEM
Most full face masks can be used for SCUBA diving or as part of a surfacesupplied system. Surface-supplied diving involves the use of a topside air supply. Air is pumped to the diver through a hose or “umbilical.” Surface-supplied diving is the preferred mode tor contaminated-water diving. It is much safer than SCUBA diving. Its advantages include an unlimited air supply, backup systems that don’t exist with SCUBA, hard-wire communications, and improved protection in contaminated-water diving.
Surface-supplied diving systems should include the following minimum components:
- Topside air supply. This can be
- either a low-pressure compressor or a high-pressure air supply with a divecontrol system that regulates the pressure. Low-pressure compressors for surface-supplied diving are bulky and heavy. They usually are driven by diesel engines and are very noisy. For most search and rescue operations, the most convenient topside air supply for surface-supplied diving is provided by ordinary SCUBA bottles, which most dive teams already have. This makes diving operations noiseless and highly portable. The backup air supply also can be high-pressure cylinders.
- Backup air supply. It must be online and ready to use in the event the main air supply fails. The air supplies are connected to provide redundant breathing systems. As the diver consumes the air in one SCUBA bottle, it is easy to switch over to the next bottle with no interruption in the breathing supply.
- Diver’s air-control manifold box. The box is used to monitor the
- diver’s breathing air supply. Both the primary and the backup air supplies connect to the diver’s air-control manifold box, which is used to control the supply of breathing air to the diver. The boxes are very easy to operate despite their sophisticated appearance. They usually are designed to accept air from a lowpressure compressor and high-pressure bottles. Many of these manifold boxes also include diver-depth monitoring systems and a communications box in one compact system.
- Communications box. This mechanism controls the communications between the diver and topside.
- Diver s hose or “umbilical ” From the diver’s air manifold box, the air supply then flows through the diver’s umbilical, a bundle of hoses that includes, at a minimum, the air hose, a communications wire, and a depth-sensing system. Depending on the type of hose used, umbilicals may be designed to float or sink. The umbilical is connected directly to the
(Photos by author.)
DIVING EQUIPMENT
- diver’s helmet through special fittings. Diving helmets are designed to keep the diver’s head completely dry and to provide protection from falling objects in the water.
Most commercial divers prefer a sinking hose, while most search and rescue teams prefer a floating hose. Floating hoses generally are lighter and easier to use in some situations, since floating hoses are less likely to become entangled, or “foul,” on underwater objects. Components used in the diver’s umbilical must be compatible with the chemical hazards encountered.
- Bail-out bottle and harness. Every surface-supplied diver wears a diver’s harness. The harness provides an attachment point for the umbilical. If the umbilical were connected only to the mask or helmet, the diver’s tender topside would be able to pull the mask off the diver’s head. In addition, the harness provides a place
- to hang any tools the diver might need to carry underwater. Many divers carry a folding rigger’s knife on the diving harness.
Also worn on the back of the diver’s harness are bail-out bottles—small SCUBA cylinders containing a sufficient quantity of air to allow the diver to reach the surface in the rare event that the topside supply is interrupted. The bottles are connected to a firststage SCUBA regulator that fastens to a special valve on the diver’s helmet. The size of the bottles is determined primarily by the diver’s working depth. In deeper dives, ice dives, or dives requiring penetration of wrecks, divers earn, larger-capacity cylinders in addition to the smaller bottles.
- Diver’s mask or helmet with communications.
SUITS
Interface. The interface between the diving helmet and the dry suit is extremely critical. Ideally, the helmet should mate directly to the suit quickly and easily, yet the connection must be positive and secure. The system should be designed so that few, if any, contaminants are trapped between the helmet and the suit when the two are separated after the dive.
Material. Dry suits for contaminated-water diving should be made from material that has a smooth, nonporous outer surface. The material must not absorb or trap contaminants. Vulcanized rubber dry suits are the most popular for diving in biologically polluted water.
Several years ago, the National Oceanic and Atmospheric Administration (NOAA) conducted tests with different types of dry’ suits in several biologically contaminated rivers. After decontamination. they found suits with a nylon fabric exterior still showed signs of bacteria for several days after the dive. In contrast, vulcanized rubber dry suits displayed almost no evidence of bacteria after proper washdown.
While vulcanized rubber dry suits help protect from most biological contamination, they do not protect against all types of chemicals or radiation. No diving helmet or suit available will turn a diver into a “superman” who w ill be sufficiently protected so that he can dive into any environment without fear of suffering consequences.
Boots. Any dry suit used in a contaminated environment must be equipped with attached boots. A suit with a thin latex sock is not acceptable. It is too easy to puncture this type of material, especially when walking on the bottom of a garbagelittered harbor.
Inflator valve. The inflator valve in a dry suit must supply a metered flow of air to the dry suit for buoyancy control and to prevent suit squeeze. It should be located in a position where it will not interfere with the diver’s harness or other equipment.
Exhaust valves. These valves automatically must vent air from the dry suit as the diver returns to the surface at the end of the dive. Manually operated exhaust valves are unacceptable for search and rescue diving—-it is too difficult to try to operate an exhaust valve while handling tools or recovering a body.
Glove systems. These systems consist of a set of cuff rings as well as the gloves (or mittens). The cuff rings come in pairs of inner and outer rings. The inner ring, machined from hard plastic, goes inside the sleeve of the dry suit at the point where the sleeve attaches to the wrist seal. The outer ring, made from rubber, slips over the sleeve and compresses the suit over the inner ring. The dry gloves or mittens snap into position over the outer ring.
INSULATION GARMENTS
Some type of insulating undergarment probably must be worn beneath the dry suit for cold-water diving (below 70°F). Water conducts heat away from the body very efficiently. Since dry suits themselves have littleinsulation capacity, the diver will chill very quickly without proper dry suit underwear.
The amount of insulation needed is determined by many factors, including body size, sex, age, water temperature. activity level during the dive, and type of insulation selected. Small divers generally chill faster than large divers and must insulate accordingly. Women usually get cold faster than men of the same size because men usually carry their extra w eight in the torso, which is where it is needed for proper insulation. Older divers usually feel the cold sooner than younger divers.
The activity level during the dive is one of the most important variables to consider when deciding on the need for insulation. The harder the work, the more heat the body produces. The dive locker should contain a variety of garments so that the diver can don or remove layers according to need. Since each individual diver has a unique physiological comfort level, it is impossible to predict how much insulation a diver requires. Divers must experiment to determine insulation requirements.
THERMAL HAZARDS
Wearing dry suits and helmets during warm weather can create thermal hazards. Kven if no dry-suit underwear is worn, the diver can overheat quickly in a dry-suit system. The hazards faced under these conditions are exactly the same as those experienced by topside haz-mat personnel during warm weather including fluid loss, heat cramps, and heat exhaustion.
DIVING EQUIPMENT
I leat stress can he a severe problem during the time the diver dresses before the dive and during decontamination. If the diver works in cold water, some of the heat stress will be relieved during the dive. Moving from very warm surface climates into cold water and then back to hot surface temperatures is stressful in itself.
for a diver working in warm water, there is no relief from heat stress, and overheating may be a very real danger. Public safety divers who work in warm waters should carefully evaluate these conditions and plan dives accordingly.
In extended contaminated waterdiving operations during warm weather, the diver’s physiology should be monitored. The heart rate, body temperature, and weight should be measured before and after diving.
Ice-filled rests. Recent experiments conducted at the National Institute of Occupational Health in Sweden evaluated the effectiveness of ice-tilled vests for cooling divers wearing dry suits similar to those used for contaminated-water diving. The vest—fitted with »6 small pockets, each tilled with a block of ice in a plastic bag—was worn underneath the suit. The divers were able to complete dives that were IS to 30 minutes longer with the ice vests. Additional tests are needed to determine safe exposure times using such systems.
TENDERS
In addition to protecting the diver, the diver’s tenders, who help in dressing and handling the diving hose, also must be properh protected. The tenders will be in the hot zone wildcat the water’s edge. They also must accompany and assist the diver throughout the decontamination procedure.
Tenders must wear the appropriate protection according to the hazard level. Besides dressing the diver, tenders must keep a firm grip on the diver’s umbilical at all times. Since they cannot leave the diver’s hose unattended, they must be provided with a sufficient air supply if the situation warrants it. The air supply must last for the anticipated duration of the dive and include a reserve supply. Tenders, too, must be protected from heat stress.
CHECKING FOR LEAKS
Once the diver is prepared to enter the water, the entire diving system must be checked for leaks. The diver may be submerged in a large vat filled with fresh water to perform this procedure. Any bubbles escaping from the diver’s suit or helmet (other than from the exhaust valve) indicate a leak. If a vat is not available, a spray bottle filled with soapy water may be used instead. Wherever air is escaping from the system, the soap will bubble.
DECON
Plans for decontamination after the dive include making sure that the appropriate decontamination equipment and supplies—including decon solutions and wash-down gear—arcon hand before the diver enters the water.
Wash-down gear may include hoses, brushes, showers, and equipment to capture the used decon solution and transport equipment for definitive decon. In cases of simple biological contamination, the diver’s equipment may be washed down in a child’s wading pool.
As the diver removes his equipment, each piece of gear should be placed in a marked container or bag. Damaged equipment may have to be discarded. As a rule of thumb, diveteams should plan on replacing onethird of any equipment used in contaminated water on an annual basis. In certain chemical environments, as we have seen, it may be necessary to discard the gear after a single exposure.
The diver himself should pass through a definitive decon shower. This is the place to remove dry-suit underwear, bathing suit, or other undergarments. These items also must be cleaned before they can be used again.
To completely clean diving helmets and other gear, the items must be disassembled. If the contaminants encountered are beyond the scope of the dive team’s ability to deal safely with the equipment, consult the manufacturer. Never return contaminated gear to a manufacturer without consent. When parts must be replaced or gear must be condemned, arrangements should be made to bill the offender responsible for the pollution that caused the damage.
Some dive teams have turned to remotely operated vehicles (ROVs) for environments unsafe for human divers. These expensive robotic devices are controlled from topside via an umbilical. The ROV, of course, must be decontaminated before it can be used again.
Diving in contaminated waters requires specialized equipment. This equipment is easy to use if divers are properly trained. Many dive teams across the United States use this gear on a daily basis. For teams that don’t, it is still important to drill and train with this equipment to be proficient in its use when it is needed.
