DIR Equipment ConfigurationA good SCUBA equipment configuration should allow for the addition of items necessary to perform a specific dive without interfering with or changing the existing configuration. Diving with the same configuration not only helps solve problems, it prevents them. Following is a list of equipment as that is of prime consideration:
- Mask: Low Volume mask reduces drag and requires less effort to clear it of water.
- Primary Regulator: Quality regulator that will be passed to an out-of-air diver.
- Short Hose: Should be long enough to breathe comfortably, but not long enough to bow and create drag.
- Back-Up Regulator: Quality regulator that a diver will use as a reserve either in the event of a failure or in an air-sharing episode.
- Long Hose: Optional in shallow, open water diving, but mandatory in deeper or overhead diving; the long hose simplifies air sharing. When used, the long hose, along with the primary regulator, should ALWAYS be placed on the diver's right post.
- Back-Up Lights: Tucked away to reduce drag but still allow for easy one-hand removal.
- Goodman Handle Light Head: Allows for hands-free diving while allowing the diver to easily direct the focused light beam.
- Thermal Suit: Appropriate to keep diver alert and comfortable.
- Crotch Strap: Allows for custom fit, and supports two D-rings: one works as a scooter attachment point; (divers should not hang equipment here as it would hang too low); and one further up, closer to the back plate, which works for towing additional gear. The crotch strap also holds the BC in position and prevents the BC from floating up away from the body.
- Hood: Where necessary to keep diver alert and comfortable.
- Mask Strap: Strong strap that will resist breaking.
- Necklace: Designed to hold the back-up regulator within easy access.
- Corrugated Hose: Should be just long enough to allow for ear clearing and potential dry suit inflation while actuating inflator, but not so long that it drags or entangles easily.
- Power Inflation Hose: Should be long enough for a diver to easily use his/her corrugated hose, but not long enough for it to bow or otherwise create excess drag.
- D-rings: No more than two on the chest, positioned to reduce the drag of attached items; one hip D-ring to hold the pressure gauge.
- Pressure Gauge Hose: Custom hose allows a diver to easily read the gauge after unclipping, but does not bow or dangle, thus avoiding excess drag.
- Pressure Gauge: Quality brass gauge should be easy to read and reliable.
- Knife: Waist-mounted in front, near the center of the diver's body, for easy access.
- Pockets: Hip-mounted to reduce drag; these pockets are ideal for storing slates, decompression tables, small guideline spools or other necessary equipment.
- Knobs: Soft knobs (to limit risk of breakage) should be opened completely.
- Valve: Contingent on environment and diving activity. Dual orifice valves (H or Manifold) are an excellent way to increase safety and redundancy.
- Burst Disks: Use of double disks prevents accidental burst failure.
- Buoyancy Compensator: Adjusted based upon needed lift whether one is diving single or double tanks. Buoyancy should be sufficient to float equipment by itself while at the surface.
- Cylinders: Contingent on environment and diving activity.
- Harness and Backplate: Designed to hold the diver snugly to their rig while reducing drag and increasing control.
- Primary Light: Hip-mounted, canister-style light; this is optional in some environments, but valuable in nearly all.
- Alternate Lift Device: Lift bag, diver alert marker, or surface life raft, for open water diving. Halcyon's MC system allows for storage in backplate pack for increased streamlining.
- Overboard Discharge: Also known as a P-Valve; used with a condom catheter by male divers to allow for urination during long dives with a dry suit.
- Bottom Timer / depth gauge: Wrist mounted to eliminate drag and entanglement.
- Watch: Wrist-mounted, with a functional stopwatch to allow for timing safety or decompression stops.
- Compass: Wrist mounted to eliminate drag and entanglement.
- Fins: These should have no attachment buckles that can break. Replace with a more robust connection.
- Guideline Reel: Use is contingent on the diving environment; it is usually mounted on the rear crotch strap D-ring for streamlining and to reduce clutter. Spools and other guideline devices are usually kept in the diver's hip-mounted pocket.
- Primary regulator: worn on the diver's back and breathed during normal diving
- Back up regulator: worn on a diver's back but not breathed (backup)
- Decompression regulator: used on a decompression bottle
- Stage regulator: used on stages typically at depth and to extend bottom time
- Argon regulator: used for suit inflation
Shallow, open water divers often use one first stage attached to a single tank. With a single regulator, the two-second stages come over the diver's right shoulder while the pressure gauge and power inflator run to the left. Diving With Two First Stages
Divers use double tanks for technical diving not only because they seek to increase their available air supply, but also because they understand the safety margin provided by redundancy. Therefore, the use of double tanks usually indicates deeper or overhead diving. Both single tank diver and double tank diver systems require the following configuration. Open water divers using a single tank should assume that all necessary hoses run from one first stage. In a doubles configuration, the primary second stage regulator is attached via a long hose to a first stage that is affixed to the diver's right post (right shoulder). This configuration not only ensures redundancy, but also facilitates gas sharing. The long hose runs straight down behind the wing, under the light canister (if one is worn, if not it is routed around the knife, or tucked into the belt), back up the left side, and around the neck; the attached second stage is then placed in one's mouth and breathed. During an emergency air-sharing episode, divers will have to unclip this regulator to pass it to an out-of-air diver. While using stage or deco bottles, donors should pass the regulator in their mouth (stage or deco) and then deploy the long hose. Should the out-of-air diver need additional decompression gas, the divers will likely take turns using the bottle (such as five minutes each) or buddy-breathe. Out-of-air divers should also be practiced in going directly to the long hose, and be able to breathe from it while it is still clipped off, deploying it later without assistance. Divers must also practice quickly deploying the long hose in a variety of situations. Divers should NEVER put their primary regulator on the left post because they risk a post roll off during contact with an overhead. Furthermore, severe contact might cause this knob to be severed in the off position, leaving the diver without a long hose in case of an emergency. Placing the long hose on the diver's right post means that the post can only be rolled open, and, in the case of a broken knob, will still be usable (both knobs turn clockwise but are on opposing sides). As with any new technique, divers may notice an early learning curve. However, a couple of dives should be sufficient for them to become proficient in managing a long hose. Whenever it is not in use divers should become habituated to clipping off their long hose to their right D-ring. While diving, hoses generally float and sit comfortably against one's body. Since, for purposes of gas exchange and general good form a diver should always be in a supine position, this long hose will usually be held in place against the body.16 Does the Long Hose Decrease Regulator Performance? Regulators can easily supply air through a long hose without registering any notable drop in breathing performance. If there is any reduction in regulator performance when using the long hose, it is negligible, and in all but the lowest performance regulators, not even a noteworthy concern. If being attached to a long hose diminishes a regulator's performance, then the regulator itself is not suitable for normal diving use. Gauges Historically, divers have been led to believe that consolidating an array of gauges into one bulky console and then dragging that console along behind them was somehow a sensible and responsible practice. Not true. By dragging a bulky console behind them, divers not only kill whatever coral they come in contact with, they also risk entanglement. Instead, divers should wear their depth gauge and compass on their wrist or forearm. In the ocean, a compass is of paramount importance, and, without interfering with other activities, needs to be viewable and held in its correct orientation on the left hand. The bottom timer/depth gauge needs to be viewable at all times and should be placed on the right hand. Mask The mask should fit comfortably, be low volume, and be of durable construction. The lenses should not remove too easily. The strap must be secure and resilient. After-market straps that substitute a neoprene-style attachment for the original may be more comfortable and are nearly unbreakable. Technical divers are often in the water for hours and sometimes carry a spare mask. A spare mask should be as small as possible while still providing a comfortable seal; stored in a pocket on the side of one's leg; and regularly checked to determine whether it is still functional. Also, to prevent the mask from fogging it should be cleaned regularly and pre-treated with a concentrated de-fogging agent before the dive. Snorkel Snorkels are useful only while divers are at the surface; during a dive they are typically in the way and pose an entanglement threat. If snorkeling, divers should choose a snorkel with a good size tube that mounts comfortably and does not offer breathing resistance. Rather than choosing from the array of gimmicky snorkels common to the dive industry, divers should learn proper skin diving techniques. Fins Stiff blade fins are popular among divers who need to swim quickly, move against strong currents, or push large amounts of equipment through water. Less rigid fins will work when pushing less equipment or when less power is desired. The best practice for divers is to use the same gear all the time. Divers should remove all plastic buckles from their new fins and substitute for them stronger attachment springs. Valves The benefits of bargain valves are questionable; therefore, divers should purchase valves of long lasting quality. Common favorites are Sherwood, Beauchat, Halcyon, and Scubapro valves. Burst ports on valves and manifolds can cause serious problems if they fail. Should these release unexpectedly underwater, a diver would rapidly lose their available air supply. Technical divers typically replace these disks with higher-pressure plugs, which should be changed yearly along with the visual inspection of the cylinder. DIN vs. Yoke Yoke valves have been around since the advent of SCUBA diving. Deutsche Industrie Norm (DIN) valves were intended to replace Yoke valves by offering a threaded design that was able to handle higher pressures. DIN valves also reduce problems by employing orifice o-rings. But, the DIN connection tube could come loose if a diver mistakenly twists the first stage to loosen the regulator-to-tank connection. For this reason, divers should only turn the hand wheel to remove the regulator. Knobs Knobs should be spring-loaded and soft, with a metal insert that prevents them from being stripped. Divers should not use metal knobs. Rubber knobs are durable, shock absorbent, shatterproof and easy to turn. Divers should be aware that, if rubbed along an overhead, rubber knobs could turn inadvertently. Plastic knobs do slightly reduce the chance of a “roll off” but can be dangerous if, on impact, they shatter. Rubber knobs—like those found on the Halcyon manifold—are very robust, while softer plastic knobs—such as those found on the Scubapro manifold—also seem to resist breaking. However, hard plastic knobs break very easily and should be replaced at once. Manifolds Manifolds are designed to connect two cylinders together to allow divers access to either or both cylinder. As divers continued to explore deep and overhead environments, it became necessary to maximize access to their gas supply, which was accomplished by attaching two first stages to one manifold. Should the regulator, o-ring, or hose fail, the diver merely shuts down the supply to that regulator, thereby preventing any further loss of gas. Because the valve knob nearest the regulator only controls flow to that first stage, the diver, through the manifold, still has access to the gas in both cylinders. In the very unlikely event of a catastrophic failure of the tank neck o-ring or the burst disk, the diver can close the isolator valve and interrupt the airflow to that side of the manifold, thereby protecting the gas supply in the other cylinder. Manifolds should have barrel-style o-rings, no face seals, and should be adjustable. The 300 bar manifold provides more threaded depth and a more secure attachment. Valves should face straight, with no angles. Manifolds that place regulators at an angle increase their exposure and elevate the risk of breaking DIN connections. Special Note About Isolator Valves on Manifolds One must always guard against accidentally turning off an isolator valve during a fill or a safety drill; a closed isolator can create problems. The isolator should always be left completely open. Symptoms of a closed isolator depend upon which tank the diver is breathing. If the gauge and “isolated” regulator are on the same tank, the diver should notice an unusually quick depletion of his/her gas supply. Divers might mistakenly believe that they are out of gas. This is unlikely (in the DIR configuration) unless the diver has had cause to breathe from the backup regulator. If the gauge and regulator in use are on opposite sides of the isolator, the gauge will continue to read the same pressure as the other tank is depleted. In this case, divers will have breathed the one tank dry and mistakenly believed that they were out of air. Realistically, this only happens to divers that are paying almost no attention to their gas supply. Unusually rapid or nonexistent depletion of gas supply is cause for evaluation and rectification. Cylinders The type of cylinder that a diver should choose depends on his/her diving environment and his/her other equipment. Improper weighting, i.e., being too positive or too negative, can be very dangerous for divers. In the ocean, an over-weighted diver with buoyancy problems could find it difficult to reach the boat, and sink ever deeper in the ocean. While in a cave, the loss of buoyancy is not as risky; nonetheless, divers could be overcome by problems associated with negative weighting. Being too positive is also very dangerous. For example, ocean divers that are too positive could not stay submerged, and would risk dangerous ascents, missed decompression, or buddy separation. In an overhead environment, positive buoyancy could make it nearly impossible for divers to stay off the ceiling and swim out of an overhead area. The goal of any SCUBA configuration is to create a system that, when empty, is as near to neutral as possible and that, when completely full, is not excessively heavy. It stands to reason, then, that at the outset of a dive, one's cylinders will be much heavier because they will be full. How heavy they will be, though, depends on the type of cylinder and the gas mixture. Proper weighting involves balancing a number of factors; these include: increased surface buoyancy, the weight of one's breathing supply, and the need to remain neutral at 10' (3m) assuming an empty set of cylinders. Furthermore, this diver must also wear enough weight to counteract an empty set of tanks near the surface where the neoprene suit will again begin to exert additional lift. The additional weight necessary to accomplish these goals could easily leave a diver nearly 40 pounds negative at depth, making a buoyancy failure a potentially serious problem.
Diver Wearing 80cf Cylinders In Full Wet Suit
Weight of Tanks with Air In Double 80's ~6 pounds
Weight Worn to Offset Neoprene Suit ~25 pounds
Total Negative Weight ~31 pounds
The basic DIR configuration uses a single primary light canister attached to the diver's hip, and two reserve lights clipped to the diver's chest D-rings where they are held to the harness by two elastic bands. The size and weight of the canister light usually depends on the particular diver's needs. Lights are optional for shallow open water diving; however, most experienced divers prefer the versatility offered by the above configuration, even for open water diving. Divers should use primary lights with a beam that can be focused for better visual reference, and a better means of communication with other team members. The primary light canister is worn on the right side of the waist belt, adjacent to the backplate, and is held securely there beneath the shoulder by either the waist belt buckle or by a second buckle that is slid up behind it. The light is part of a diver's weight and balance, and should be placed under the shoulder where it is protected and out of the flow, and can be conveniently operated or removed if necessary. This location not only keeps the light canister from interfering with a diver's kicking movement, but also places it in the same water column as the one broken by the diver's shoulder as s/he moves through the water. This insures that the light is streamlined and does not impede a diver's progress through the water. When the light is in use, the light head should be held in the left hand. When the light is not in use or when one's hands are needed to switch to a stage bottle or to a decompression bottle, the light head should be clipped off to the right chest D-ring. Some people believe that divers with hip-mounted lights cannot efficiently wear multiple stage bottles. A glance at the configuration of today's most active explorers will suffice to put these concerns to rest. In such a configuration, a multiple stage dive is conducted with all stage bottles located on the left side of the body, opposite the light canister. Reserve Lights
Reserve or back-up lights are key components of the DIR gear configuration. These lights must be reliable, streamlined and conveniently stowed. Following a primary light failure in an overhead environment, the diver must switch to the reserve light and initiate an exit. Reserve lights whose burn times equal a diver's total bottom time would be excellent choices.22 While primary lights should contain rechargeable batteries, reserve lights should contain disposable batteries (more reliable, consistent and predictable). Reserve lights should be stored on the harness below the arms, where they tuck neatly out of the way and are essentially snag-free. A diver with a primary light failure can easily turn on the reserve light before removing it. The benefits of this are clear; if the light has been turned on before it is unclipped and dropped it can be easily found. Also, another advantage of positioning the reserve light in this manner is that it can be activated and left clipped off while one is managing other equipment. Stage/Decompression Bottles A stage bottle is a bottle used to extend bottom time, whereas a decompression bottle is a bottle used during the ascent portion of the dive to promote efficient decompression by reducing inert gases (e.g., N2 and He) while elevating oxygen percentages. Stage and decompression bottles are almost exclusively used in technical diving, where longer bottom times and/or multiple gas mixes are the standard. These bottles usually rely on the same or similar equipment and are filled with appropriate gases for a given dive. While ocean diving, stage and decompression bottles should be made of aluminum so as to not overweight the diver. Cylinders as small as 40cf are usually perfectly adequate for most ocean decompressions, with 80cf cylinders being the permissible upper limit. In cave diving, where decompression bottles are left behind in the spring basin, steel bottles are appropriate. Cave divers usually prefer steel bottles' lower working pressure providing them with a better volume of oxygen for the given pressure (i.e., a steel 95cf bottle contains 95cf of oxygen at 2,640psi, whereas at 2640psi a 80cf cylinder will only hold 72cf of oxygen). In cave diving, the decompression cylinders of choice are steel 72's or steel 95's for oxygen, and aluminum 80's for Nitrox mixes. All stage and decompression bottles should be rigged with stainless steel bolt snaps; what size these will be is determined by whether or not one's diving requires gloves. Steel bolt snaps are attached by a piece of 1/4” line run under a hose clamp placed halfway down the tank. The upper bolt snap should be placed slightly above the break of the neck and sit snugly against the tank. The lower bolt snap should be affixed to the 1/4” line that will extend beyond the hose clamp. This tie point for the snap should be near the middle of the bottle (roughly 16 inches between clip attachments). To prevent drag, the bottle needs to be held close in the front and relatively loose in the back. If the bottom clip is placed too low or is affixed too tightly, then the bottom of the bottle will be pulled higher, and will form a wedge with the front of the bottle. Cylinders should float horizontally and sit parallel to a prone diver. There should NEVER be any metal-to-metal connections of any part of one's equipment. Stage bottle clips MUST be able to be cut free should the clip jam or the bottle become entangled. All bottles should be permanently marked to reflect their maximum operating depth (MOD), using three-inch high letters placed horizontally in the orientation of the tank. Furthermore, tanks should be marked on both sides to allow both the diver and his/her buddy to take note of the depth, regardless of tank position. A decompression or stage bottle regulator is fitted with a short pressure gauge bent back on itself to face the diver, and is held in place, at the first stage, by bungie cord. Its regulator hose must be "octopus length", or 38” (96cm). When not in use, regulators are always tucked away in an elastic band on the bottle, and the bottle turned off. To facilitate streamlining and one-hand valve management, decompression/stage bottles are generally worn on the left side. Wearing bottles on both sides forces a diver's arms into a bulky “muscle man” posture and greatly limits flexibility. In addition to limiting diver flexibility, stages on a diver's right side interfere with efficient DPV piloting. To deploy a bottle, divers should carefully adhere to the following procedure:
- Divers should operate as a team, verifying proper mixture and depth.
- Arrive at the desired switching depth, retrieve and attach the cylinder if required.
- Locate the properly marked cylinder and deploy its second stage. Open the valve completely.
- Each diver should double-check their buddy's cylinder depth and the second stage used.
- Remove regulator from the mouth and replace with stage regulator.
- Grab the second stage hose and retrace it back to the stage cylinder.
- Double-check cylinder marking.
- If beginning decompression, start decompression time.
- Dive computers tend to induce significant levels of diver dependence, and undermine the awareness essential to all diving, but particularly essential to divers just beginning decompression diving.
- Dive computers prohibit proper planning; they discourage divers from “studying” the impact of various mixtures and decompression choices.
- Dive computers are of little educational benefit because they promote neither questioning nor proper planning discussions.
- Dive computers often use algorithms that heavily pad decompression time; this sometimes results in odd and ridiculous levels of conservatism.
- Dive computers are expensive, and prevent divers with limited resources from purchasing truly useful equipment.
- Dive computers significantly limit the likelihood that divers will track their residual nitrogen groups, leaving them less informed in the event of computer failure.
- Dive computers do not allow for diving helium in any format but the bulkiest and most questionable. It is very likely that new helium-based decompression computers will be inordinately conservative and suffer from all the limitations of air and Nitrox dive computers.
- Dive computers often generate longer decompressions than an astute, well-educated, experienced diver generates.
- Dive computers often confuse matters by providing the diver with too much useless information, sometimes even obscuring depth and time in favor of blinking CNS and/or decompression limitations.
- Some dive computers become very difficult to use if a decompression stop has been violated. Some computers will lock up completely, while others will just beep or generate erroneous and distracting information.
- Dive computers do not allow the educated diver to properly modify his/her decompression profile to account for advances in knowledge, e.g., the use of deeper stops in a decompression profile.
- Dive computers do not offer divers much flexibility to generate profiles with varying conservatism. For example, the right mix would allow 100 minutes at 60 ft rather than 60 minutes at 60 ft, but a diver might prefer to do one or the other or a hybrid of the two. Computers confuse this issue by not providing divers with the proper information.
- Dive computer users often ignore table proficiency and therefore do not learn to read tables properly. When faced with a situation where they can't dive a computer (e.g., failure or loss) these divers are seriously handicapped.