A diver experiencing a primary light failure can easily turn on the reserve light prior to its removal. The benefit is clear: if dropped, this light can now be easily retrieved. Also, the reserve light can be activated and left affixed while managing any other equipment issues. Lights located on the harness below the arms are easier to remove, easier to activate, easier to replace and do not require additional equipment like clamps and D-rings on the tank
Reserve or back-up lights are key components of the DIR gear configuration. These lights must be reliable, streamlined and conveniently stowed along the MC's harness straps. Following a primary light failure in an overhead environment, the diver must switch to the reserve light and initiate an exit. The time spent using the reserve light should not be much greater than half of the diver’s bottom time; however, a reserve light should be able to provide more time in the event of a delayed exit. Reserve lights that are capable of burning for the length of a diver’s total bottom time are sufficient. While the primary light should contain rechargeable batteries, the reserve lights should contain disposable batteries. These batteries have a more reliable burn time and will provide consistent and predictable results. Replace the batteries in the reserve light after each significant use. If it has not been used in six months, replace the batteries with a fresh set. The old batteries should be fine for household use, but are no longer reliable for critical life-support equipment.
1. Burn timeThe Backup light must have sufficient burn time to equal the expected bottom time. 2. Avoid rechargeable batteries Back up lights should not use rechargeable batteries as they tend to have a more unreliable burn time when not frequently used. 3. AccessibilityReserve lights should be easily accessed and configured in a streamlined or unobtrusive manner. When the primary fails you need to be able to immediately locate the backup light. 4. Stowage The light should be turned on before being detached from the harness. If dropped it can be easily retrieved. 5. Keep it in viewDo not conceal the light in a pocket or pouch if accidentally turned on. It will not be seen. 6. Keep it neatLook for smaller, less obtrusive lights. These lights are not as likely to snag on line or other objects such as the in line three c cell light. Using a light larger than a four c cell light is likely to be too cumbersome. 7. It needs to be toughMake sure that the light is rugged and not prone to easy damage. If it seems cheap it probably is.