Table 16-4 Detection Systems scrubbers must not be allowed to overheat. In an attempt to replace carbon dioxide as a gaseous fire quenching agent, both nitrogen and helium have been considered and tested. It appears that neither of these inert gases is of value (except by the rapid dilution method in which the entire chamber atmosphere is rapidly diluted), as it is not possible to maintain a significant concentration of the gas in a given location. Due to their narcotic properties, more research is needed before the gases of heavier molecular weight can be considered for such use under pressure. Although dry chemical agents should provide rapid suppression of flame and excellent radiation shielding when initially discharged, the permanency of the fire extinguishment is doubtful. Although monobromotrifluromethane (CBrF3, "Freon" 1301) and chlorobromomethane ("Freon" 1011) have been shown to be effective extinguishing agents, a delayed application of the extinguishing agent could produce toxic pyrolysis products if the fire had a head start. High expansion foam has been shown to be an effective means of extinguishing fires that have been allowed to build up to their full intensity, but there is presently little knowledge as to the physiological safety of such agents due to pyrolysis products or otherwise. At the present "state of the art", due to safety considerations, the best extinguishing agent for use in hyperbaric chambers is water. Water extinguishment operates primarily by cooling. It works best if it strikes the flame or wets the fire, but wetting most substances will retard to prevent their burning, even in oxygen. In spray form, although the fire may not be immediately put out, spread is halted and from this point on extinguishment is almost certain. The spray can be continued indefinitely, assuring safety of chamber occupants. Water at a spray density of 5 milliliters per sq cm per minute (14 gallons per sq ft per minute), applied for two minutes is required to extinguish cloth burning in 100 percent oxygen at atmospheric pressure. Water spray systems require special design for hyperbaric chamber applications. The pressure at the spray nozzles must be about 50 psi above chamber pressure to produce the desired degree of atomization and droplet velocities. Spray pattern of nozzles might be affected by chamber pressures. To compensate for the reduced coverage at elevated pressures, the design of the system must provide an adequate number of nozzles, and they must be strategically located, to wet all possible exposed areas within the chamber no matter what the chamber pressure may be. Pressurization is best obtained from a compressed gas source, since pumps have a startup time. Simultaneously with discharge of the water, all electrical power to the chamber should be discontinued to pre It is imperative that water deluge systems be thoroughly tested at all applicable operating pressures and conditions. Numerous installations have been disappointing when given realistic tests, and redesign has been necessary. 16.4.7 General Safety Procedures 1. Maintain oxygen concentration and/or partial pressure as low as possible, preferably within the region of non-combustion. Use an overboard dump system where pure oxygen is breathed by mask in a chamber. 2. Eliminate ignition sources. 3. Minimize combustibles, with the complete exclusion of flammable liquids and gases. 4. If combustible materials must be employed. the type, quantity and arrangement in the chamber must be carefully controlled. 5. Fire walls and other containment techniques should be utilized to isolate potential high risk fire zones. 6. A fixed fire extinguishing system should be utilized which incorporates automatic initiation by flame and smoke detectors as well as manual initiation and provides rapid and sufficient agent discharge. 17.0 GENERAL First aid is the immediate, temporary assistance provided a victim of injury or illness before the services of a qualified physician can be obtained. Its purpose is to save a victim's life and to prevent further injury or a worsening of his condition. When an accident occurs, a knowledge of the proper response can mean the difference between life and death, temporary or permanent disability, or shortor long-term hospitalization. All individuals associated with diving should have a thorough understanding of the basics of first aid. When an injury occurs an immediate, correct response is required. It is not the time to be looking for a book that tells you what to do. A matter of seconds can mean the difference between life and death. This section is not intended to serve as a definitive treatise on first aid, but rather as a general guide to the handling of diver related accidents. The reader is referred to the Standard First Aid and Personal Safety Manual of the American Red Cross 1973. 17.1 INTRODUCTION TO FIRST AID PROCEDURES In administering first aid, it is essential to maintain critical vital functions these are: stopping bleeding, determining cardiac status or femoral pulse, and assuring an adequate airway. All three may have to be dealt with simultaneously. Copious bleeding is the first and most important problem to contend with. Bleeding must be terminated quickly as a human can bleed to death in as little as 3 to 5 minutes. An accident victim will be able to survive longer without breathing or heart beat than if his blood is allowed to be pumped from his body. If the victim is not breathing, mouth-to-mouth resuscitation must begin (See Paragraph 17.1.3 and Figure 17-1). Closed chest cardiac massage should be administered also for cardiac arrest (See Paragraph 17.1.2). Also, all serious injuries will be accompanied by shock. This complication can be as serious as the actual injury and must be dealt with quickly. These three factors always require prompt action and are most important in saving a victim's life. An unconscious diver should always be presumed to have an embolism unless another cause of the unconsciousness can be established quickly (within a few minutes). If an embolism is suspected, the first action is to get the victim into a recompression chamber and under a pressure equivalent to 165 feet as quickly as possible. First aid for other injuries can be administered while proceeding to, or while in the chamber. Another important factor in administering first aid and one often overlooked is the attitude of the person administering the aid. He should work to inspire the victim's confidence by presenting a panic-free appearance. In serious injuries, telling a victim the extent of his injuries should be avoided. Instead, try to assure him that he will be all right. Knowledge of the actual extent of injuries could cause unnecessary excitement and panic causing complications of the injury and deepening of shock. 17.1.1 Bleeding In diving, the causes of bleeding are numerous, and in some cases may be an indication of other, more serious injuries. Bleeding from the mouth, nose and ears is a good indication of some form of pressure related accident. If the diver is unconscious with nonfrothy blood coming from his mouth, he probably bit his tongue during the convulsions which accompany oxygen toxicity. Should the diver be unconscious and passing frothy blood from the mouth, it is probably an air (gas) embolism, and should be treated as such. A conscious diver in |