What an inertia reel is, and what it is not
Inertia reel, self retracting lifeline, SRL, retractable fall arrester and fall arrest block all describe the same class of device. The name changes by brand and by trade, not by function. Australian sites and suppliers most often use inertia reel, manufacturers most often use self retracting lifeline, and the two are interchangeable when specifying equipment.
What separates an inertia reel from a shock absorbing lanyard is the length of line in play. A lanyard is a fixed length, usually 1.8m or 2m, and it needs enough clearance below the anchor for the line, the deployed energy absorber and the worker's height. An inertia reel keeps the line taut as the worker moves, so there is very little slack to fall through, and it arrests the fall in a shorter distance. That is why an inertia reel is the answer where clearance is limited and a lanyard is not.
What an inertia reel is not is an adjustable lanyard. The line retracts under its own spring tension and cannot be set to a working length. Nor is it a restraint device. Restraint equipment prevents a worker reaching an edge so a fall cannot occur, and it does not need an arrest mechanism at all.
Choosing a length and a line
Two decisions come first, and everything else follows from them.
Working length. Personal SRLs are around 2m and are designed to be worn on the harness, usually paired so the worker stays connected while moving between anchor points. Mid length units of roughly 6m to 15m mount to an overhead anchor and cover a work area. Long line units of 15m to 33m are for tower work, shafts and confined spaces where the worker moves through height rather than across a floor.
Line type. Webbing units are lighter and easier to handle, which matters when the device is worn rather than mounted. Galvanised cable units are more resistant to abrasion and contamination and last longer in dirty environments. Stainless cable is for coastal, marine and chemically aggressive sites. The line type, not the brand, is the durability decision.
Sharp edge, environment and rescue capability
Three specification decisions separate devices that otherwise look alike.
Sharp edge rating. A standard inertia reel is designed to be anchored overhead, where the line does not bear against anything. If the anchor is at or below foot level, or the line can cross a roof edge, a parapet or structural steel, the device must be specifically rated for use over an edge. This is tested against a defined edge radius and it is a per product declaration, not a category assumption. Check the manufacturer's statement on the product page before ordering.
Environment. Sealed units are built for corrosive, dusty and washdown environments where an open housing will fail. They cost several times a standard unit and they exist because replacing a failed device is more expensive again.
Rescue capability. A retrieval block carries an integrated winch, so a fallen or incapacitated worker can be raised or lowered without a separate rescue system. Confined space work, tank entry and shaft work generally require it. If the job has a rescue plan that depends on retrieving the worker through the same opening they entered, the device needs the winch.
Harnesses, anchors and inertia reels
An inertia reel is one part of a three part system, and the three parts are specified together. The harness distributes the load across the body, the inertia reel arrests the fall, and the anchor point holds both. An inertia reel bought without confirming the rating of the anchor it will hang from is a device bought on trust.
Height Safety Central supplies all three. The harness range covers full body, EWP, rope access and confined space harnesses. The anchor range covers permanent, temporary and roof mounted anchor points. Personal SRLs are usually bought in pairs and worn on the harness, so a buyer specifying one is normally specifying the harness at the same time.
