Lights for Cave Diving

 

Lights

Recreational dive lights and cave diving lights have the following in common: they both emit light; they both work under water. At this point similarities end.

 

 

 

Goals

 

  What you will be able to do
at the end of this section
What this ability
will do for you
List three reasons why the typical recreational dive light is inadequate for cave diving. These abilities will help you select the proper lighting systems for cave diving,
Identify the features that give modern cave lights the necessary power, duration and versatility.
Identify the proper number of battery powered back-up lights for cave diving and explain their role in cave diver safety.

 

Where Recreational Lights Come Up Short

 

The typical recreational dive light consists of a self-contained light head, comprising both the power supply and bulb. Attached to the light head will be a handle — usually a pistol grip style unit. Finally, to attach the light to the user's wrist, there will be a lanyard. All of these elements combine to make the typical recreational dive light totally unsuitable for cave diving. Recrational Dive Light
Very Dark Having the bulb and power supply contained in a single unit limits their potential output. The typical recreational dive light does a poor job of illuminating large cave passageways (although this is changing somewhat as HID technology migrates to recreational dive lights).
The combination of a large light head and pistol grip make the light impossible to use with guideline reels, as there is simply no way to hold both the light and reel in the same hand while deploying or retrieving the guideline. Light and Reel
Dangling Light The lanyard presents yet another entanglement hazard, and makes it difficult to temporarily store the light elsewhere when the user needs both hands free.

 

Cave Diving Lights

Cave diving lights have evolved to overcome these limitations and meet the specific needs of cave divers.

 

Cave diving lights consist of a waist-mounted battery canister, connected by a power cord to a separate, compact light head. Because this configuration allows the use of larger power supplies, cave diving lights can burn brighter and last longer. HID Light
Hand Mount Because the compact light head can be worn on the back of the user's hand, it will not interfere with reel use or other tasks.
Modern cave diving lights are powered by a 12-volt Nickel Metal Hydride (NiMH) or lead-acid (gel cell) rated at 4 amps or greater. Their light heads employ a 10-watt or larger High-Intensity Discharge (HID) bulb, encased in a waterproof, test-tube-style lens and surrounded by a compact, focusable reflector. Light Head and Battery
Burn Times Innovations such as NiMH batteries and HID bulbs enable today's cave diving lights to be substantially smaller and lighter than their predecessors of just a few years ago. At one time, the typical cave diving light consisted of a battery canister the size of a large Thermos, powering a 50-watt quartz-halogen bulb. It would have a theoretical "burn" time of three hours or less. In contrast, a modern 10-watt HID bulb outputs roughly the same amount of light — at a much higher color temperature — and can last up to four hours or more when powered by a NiMH battery canister the size of a Coke can.

 

Back-Up Lights

 

Another area in which recreational and cave divers differ when it comes to lighting is the use of backup lights. Despite recent innovations, dive lights remain among the least reliable pieces of equipment divers carry. For this reason, cave divers carry two additional battery-powered backup lights in addition to their primary. These compact units are typically powered by four AA or three size C alkaline cells. Back-Up Light
Burning Out Recreational divers are taught to carry at least one such backup light. Unfortunately, many do not. This is one of the contributing factors to the more than 300 incidents in which divers without proper cave training have perished in underwater caves.

Key Points

Can you answer these questions about cave diving lights? »

 

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