D-ring extensions allow easier access to the dorsal D-ring without having to go through the yoga contortions sometimes required to hook up your fall protection, but these extensions are not for every situation and must be used with care. Adding extra length to fall protection can result in additional swing forces acted upon the climber in the event of a fall. That makes intuitive sense. You're making the pendulum longer, so the swing could be wider. Using an extender may be allowed with lanyards, but in our experience, self-retracting lifelines (SRLs) provide a safer combination with these devices. SRLs will take up the slack in the lifeline, so it shouldn't change the actual fall distance unless you're working right up against your anchor point.
Conditions in the field vary widely, so guidance is given relative to acceptable practices. If you want to dig through DBI's technical info sheet on web and rope lanyard uses, click here. To break down the basics, the longest standard shock absorbing lanyards are 6 feet in length. While it may be possible to buy longer sizes, the user is responsible to make sure that they keep that fall distance at 6 feet or less. There is an exception made when the tie-off point is at your feet, such as on a scissor lift, and special lanyards with extra shock absorbing capacity are used in that case.
Ideally, as we noted, you will be using a SRL, as this will consistently take up any slack in your connection system, and limit your fall distance. We find that the sales on typical shock absorbing lanyards are declining, with a corresponding increase in SRL sales. If you look at fall distance calculations on shock absorbing lanyards vs. using an SRL, it is easy to see why.
Another important note about D-ring extenders - don't add anything else to your harness D-ring if you are using an extension device. This means secondary fall protection, if you're using it, needs to be attached to the front D-ring or shoulder rings, if you're using a rescue harness.
If you have questions about your specific application and whether it's safe to use a D-ring extender, don't hesitate to call us at 1-800-829-9580.