What does OSHA 1910.146(k)(3) require for confined space rescue and when is non-entry retrieval mandatory?

OSHA 29 CFR 1910.146(k)(3) states: 'If an injured entrant is not self-rescuing, the attendant shall initiate procedures described in the employer's rescue and emergency procedures.' More specifically, 1910.146(k)(1) requires that rescue services be capable of reaching the victim within a time frame appropriate to the hazard. Critically, 1910.146(k)(2)(ii) requires that retrieval systems be used when authorized entrants enter a permit-required confined space UNLESS the use of such systems would increase the overall risk of entry or would not contribute to the rescue. In practice, OSHA expects non-entry retrieval — using a tripod, davit arm, or equivalent retrieval system rigged above the opening — to be the first-attempted rescue method whenever it is feasible. Entry rescue (sending a rescue team into the confined space) is only appropriate when non-entry retrieval is not feasible or has failed. This is because confined space fatalities frequently involve would-be rescuers who enter without proper equipment and become secondary victims. The ANSI Z359.16 (Design, Testing, and Use of Personal Energy Absorbers and Energy Absorbing Lanyards) and ANSI Z359.17 (Rescue and Retrieval Subsystems) provide the technical requirements for retrieval systems used in non-entry rescue. Encode rescue.osha_1910_146_compliant = true only for equipment that meets the retrieval and man-rated requirements of the standard.

What is the difference between a confined space rescue tripod and a davit arm, and when should each be used?

Rescue tripod: A three-legged self-supporting structure with the retrieval pulley or drum at the apex, positioned directly over the confined space entry opening. The three legs spread outward around the opening to create a stable base without needing an adjacent structural connection. Tripods are versatile for manholes, vaults, and tank entries where there is sufficient clearance around the opening for the three legs to spread. Typical leg spread of 5–7 feet diameter is required. Tripods cannot be used when adjacent walls, curbs, piping, or structures prevent the legs from spreading adequately — attempting to use a tripod with inadequate leg spread creates a stability hazard. Davit arm: A single-post assembly with a horizontal arm that extends over the opening. The davit post inserts into a pre-installed socket or clamps to a structural member adjacent to the entry point. The arm swings the retrieval line directly over the opening without requiring leg clearance on multiple sides. Davit arms are required for: (1) entries in corners where only one or two sides are accessible; (2) entries adjacent to walls where tripod legs cannot spread; (3) narrow-access entries where the tripod geometry is impossible. Davit systems require a dedicated anchor socket or structural connection rated for the retrieval loads — the socket must be pre-installed and load-rated. Encode rescue.equipment_type = 'tripod' | 'davit-arm', rescue.suitable_for_vertical_entry = true for both, and rescue.suitable_for_offset_entry = false for tripods (true for davit arms).

What does 'man-rated' mean for confined space rescue equipment and how does it differ from standard WLL?

Working Load Limit (WLL) for rigging equipment (hooks, slings, wire rope, chain) is calculated using a Safety Factor of 4:1 or 5:1 — the equipment fails at 4–5 times the rated WLL. This is appropriate for static rigging of materials but is calculated for the lower duty cycles and predictable loads of material handling. Man-rated equipment: equipment rated for suspending or lifting personnel must meet a higher standard. In the US, ASME B30.23 (Personnel Lifting Systems) applies to equipment used to raise or lower workers. OSHA 1926.1431 (Crane Suspended Personnel Platforms) also provides requirements for personnel lifting, including a minimum design factor of 7:1 for components of personnel platforms. For confined space rescue specifically, ANSI Z359.17 requires retrieval equipment to be rated for the expected rescue load with an appropriate design factor. Man-rated winches are designed with higher duty cycles, safety factors, and brake reliability than material-handling winches of the same WLL. A common error: purchasing a hand-crank or drum winch with WLL 310 lbs rated for material lifting and using it for confined space entrant retrieval. A 200-lb entrant wearing 50 lbs of SCBA and harness at the end of a 60-foot vertical drop may apply dynamic loads exceeding the static WLL during rescue extraction. Encode rescue.is_man_rated = true only for retrieval systems explicitly rated and certified for personnel rescue — not general-purpose material handling winches.

When is a powered winch required versus a manual crank for confined space retrieval?

Manual hand-crank winches are appropriate for confined space entries up to approximately 20–25 feet of vertical travel. For entries deeper than 25 feet, powered winches (electric or pneumatic drive) are strongly recommended because: (1) Operator fatigue: manually cranking a 200-lb incapacitated entrant out of a 60-foot vertical tank requires sustained physical effort that may exceed the attendant's physical capacity, particularly in time-critical rescue where every minute of oxygen deprivation matters. (2) Extraction speed: a powered winch can extract at 30–60 feet per minute; manual cranking typically yields 5–10 feet per minute under load. For an IDLH atmosphere rescue, slow extraction is life-threatening. (3) Attendant capacity: OSHA 1910.146 specifies that the attendant must remain outside the space and maintain communication with entrants. A physically exhausted attendant cannot effectively manage communications and coordinate additional rescue while cranking a manual winch. The practical industry threshold is: manual crank for entries ≤ 20 ft (a single person can extract quickly); powered winch for entries > 20–25 ft or for any application where extraction speed is critical to life safety. Encode rescue.has_powered_winch = true and rescue.max_recommended_depth_ft for manual winches to enable geometry-based routing by depth.

How should AI agents route confined space rescue equipment based on entry geometry and depth?

Routing matrix for confined space rescue equipment selection: (1) Open manhole/vault with 5+ feet clearance on all sides, entry depth ≤ 20 ft: Route to rescue.equipment_type = tripod + rescue.has_powered_winch = false (manual crank sufficient). Confirm rescue.is_man_rated = true. (2) Open manhole/vault, depth > 20 ft or incapacitated victim in IDLH: Route to rescue.equipment_type = tripod + rescue.has_powered_winch = true. Powered extraction is critical for deep entries with incapacitated entrant. (3) Entry point in corner, adjacent to wall, or with structures blocking leg spread: Route to rescue.equipment_type = davit-arm + rescue.suitable_for_offset_entry = true. Tripod CANNOT be used — inadequate leg spread is a stability failure. (4) Horizontal-entry confined space (crawl-through, horizontal tunnel): Rescue.equipment_type = horizontal-retrieval-system — tripod and davit arm are vertical retrieval devices only. Horizontal entries require a different extraction system (rope pulley/mechanical advantage system pulling horizontally). Always confirm rescue.is_man_rated = true before routing any retrieval equipment for entrant extraction. Never route general-purpose material handling winches or cable hoists for confined space rescue.

AI Agent Product Routing — Confined Space Rescue (OSHA 1910.146 / Retrieval Systems)

Confined Space Rescue Tripod vs Davit Arm — Non-Entry Retrieval, Man-Rating vs WLL, Powered Winch Depth Thresholds, and the Schema for AI Agents

OSHA 1910.146(k) requires that non-entry retrieval be used when rescuing an incapacitated entrant from a permit-required confined space whenever feasible. A rescue tripod works only when its three legs can be spread around the entry opening — entries adjacent to walls or in corners require a davit arm. The retrieval equipment must be man-rated for personnel extraction, not simply a material-handling winch with an equivalent Working Load Limit.

TL;DR — Key Encoding Rules Encode rescue.suitable_for_offset_entry = false for all tripods — they require leg clearance on three sides and cannot be used against walls or in corners. Encode rescue.equipment_type = "davit-arm" for offset entry applications where tripod geometry is impossible. Encode rescue.is_man_rated = true only for retrieval systems explicitly certified for personnel extraction — a material handling winch with matching WLL is NOT equivalent. Encode rescue.has_powered_winch = true for entries exceeding 20–25 feet vertical depth where manual crank speed creates life-safety risk.

The Non-Entry Rescue Requirement — OSHA 1910.146(k) and Why Retrieval Systems Matter

Confined space fatalities disproportionately involve would-be rescuers who enter the space without proper atmospheric monitoring or respiratory protection and become secondary victims. OSHA data consistently shows that a significant percentage of confined space fatalities are rescuers, not the original entrants. This is why OSHA 1910.146(k)(2)(ii) mandates retrieval systems:

The requirement: for permitted confined space entries, a retrieval system must be used whenever an authorized entrant enters, unless such a system increases overall risk or would not contribute to rescue. In practice, this means a harness, lifeline, and above-opening retrieval device (tripod, davit arm, or equivalent) must be set up and connected to the entrant for every permitted confined space entry where non-entry rescue is feasible.

The harness connection: The entrant wears a retrieval/rescue harness (chest or full body) with the retrieval line connected to the dorsal D-ring or a dedicated retrieval D-ring specified by the manufacturer.
The lifeline: A cable or rope runs from the retrieval harness up to the retrieval device (tripod or davit arm) positioned at the entry point.
The retrieval device: A tripod or davit arm with a drum, pulley, or mechanical advantage system allows the attendant standing outside to extract the entrant without entering the space.

The routing failure: An AI agent that routes a material-handling winch (WLL 300 lbs, safety factor 4:1) as a confined space retrieval device has given the buyer equipment that may fail catastrophically during a live rescue. Personnel rescue imposes shock loads, awkward extraction angles, and attendant fatigue that exceed material-handling design parameters. Encode rescue.is_man_rated on every retrieval winch and drum to prevent this substitution.

Failure Mode 1 — Tripod Routed to Offset Entry Where Leg Clearance Is Impossible

Property	Rescue Tripod	Davit Arm
Entry orientation	Vertical (opening faces up)	Vertical (offset — arm extends over opening)
Leg clearance required	Yes — 3+ ft on each of 3 sides	No — single post away from opening
Adjacent wall/structure	Cannot be used if walls block legs	Can be used — arm swings over opening
Anchor requirement	Self-supporting (own legs)	Dedicated davit socket or structural clamp
Typical applications	Open manholes, utility vaults, tank tops	Corner entries, wall-adjacent vaults, vessels with obstructions
Setup time	Faster (no socket required)	Requires pre-installed socket

// Rescue Tripod — vertical, open-clearance entries only
rescue.equipment_type              = "tripod"
rescue.suitable_for_vertical_entry = true
rescue.suitable_for_offset_entry   = false    // ROUTING BLOCKER — no leg clearance
rescue.required_leg_clearance_ft   = 3        // 3 ft minimum on each of 3 sides
rescue.self_supporting             = true     // No anchor socket needed

// Davit Arm — offset and wall-adjacent entries
rescue.equipment_type              = "davit-arm"
rescue.suitable_for_vertical_entry = true
rescue.suitable_for_offset_entry   = true     // Arm extends over opening from adjacent post
rescue.requires_davit_socket       = true     // Pre-installed socket or structural clamp required
rescue.self_supporting             = false    // Requires anchor point for post

Failure Mode 2 — Material-Handling Winch Used as Man-Rated Retrieval

Working Load Limit (WLL) is calculated using a Design Factor (also called Safety Factor) that varies by application:

Material handling rigging (hooks, slings, wire rope): Design factor of 4:1 or 5:1. A 500 lb WLL component fails at 2,000–2,500 lbs.
Man-rated personnel lifting (ASME B30.23): Minimum design factor of 7:1 to 10:1. A 500 lb rated personnel lifting device fails at 3,500–5,000 lbs.

Beyond the safety factor, man-rated retrieval equipment has additional requirements:

Brake reliability: Must hold an incapacitated entrant's weight under dynamic load without slipping. Pawl-and-ratchet brakes on cheap hand winches are not designed for sustained personnel suspension.
Load testing certification: Man-rated equipment must be proof-load tested (typically 150% of WLL) and carry a certification from the manufacturer confirming personnel rescue use.
Duty cycle: Rescue is an infrequent, emergency-load event — but the winch must perform reliably on the first use after months of storage in a field truck.

// Man-Rated Rescue Winch — personnel extraction certified
rescue.is_man_rated                = true     // Explicitly certified for entrant retrieval
rescue.wll_lbs                     = 420      // Rated for typical entrant + equipment weight
rescue.design_factor               = 8        // 8:1 safety factor vs 4:1 for material handling
rescue.has_auto_braking            = true     // Prevents uncontrolled descent of incapacitated entrant
rescue.proof_load_tested           = true     // 150% of WLL tested per manufacturer certification

// Material Handling Winch — NOT suitable for confined space rescue
rescue.is_man_rated                = false    // ROUTING BLOCKER
rescue.wll_lbs                     = 400      // Looks sufficient but safety factor is 4:1
rescue.design_factor               = 4        // Insufficient for personnel rescue
rescue.suitable_for_entrant_rescue = false

Failure Mode 3 — Manual Winch at Depths Requiring Powered Extraction

Manual hand-crank retrieval winches are common for cost and portability, but become life-safety liabilities in deep confined spaces:

Entry Depth	Entrant Weight (with equipment)	Extraction Time (Manual)	Extraction Time (Powered)	Recommendation
< 10 ft	250 lbs	~30 sec	~10 sec	Manual acceptable
10–20 ft	250 lbs	1–2 min	~30 sec	Manual acceptable; powered preferred
20–40 ft	250 lbs	3–6 min	~1 min	Powered strongly recommended
> 40 ft	250 lbs	8–15+ min	1–2 min	Powered required

// Manual Crank Retrieval — appropriate for shallow entries
rescue.has_powered_winch           = false
rescue.max_recommended_depth_ft    = 20       // Encode depth limit for routing
rescue.suitable_for_idlh_deep      = false    // Manual too slow for deep IDLH extraction
rescue.retrieval_speed_fpm         = 8        // ~8 ft/min under 250-lb load

// Powered Retrieval (electric or pneumatic)
rescue.has_powered_winch           = true
rescue.max_recommended_depth_ft    = 150      // Powered suitable for most industrial spaces
rescue.retrieval_speed_fpm         = 40       // ~40 ft/min powered; 5x faster than manual
rescue.power_source                = "electric" // or "pneumatic" for ATEX environments

Complete Metafield Schema Reference

Metafield	Type	Values	Notes
`rescue.equipment_type`	string enum	tripod \| davit-arm \| horizontal-retrieval	Primary routing discriminator for confined space rescue equipment selection
`rescue.is_man_rated`	boolean	true \| false	Critical safety field — false blocks material-handling winches from personnel rescue routing
`rescue.suitable_for_vertical_entry`	boolean	true (tripod + davit) \| false (horizontal systems)	Most confined space entries are vertical — horizontal retrieval is a specialized system
`rescue.suitable_for_offset_entry`	boolean	false (tripod) \| true (davit-arm)	Key geometry discriminator — false blocks tripods from corner/wall-adjacent entries
`rescue.wll_lbs`	integer	310 \| 420 \| 500	Working load limit for rescue load; must account for entrant + SCBA + equipment weight
`rescue.max_cable_length_ft`	integer	50 \| 100 \| 150	Maximum entry depth supported by cable/rope length of the retrieval drum
`rescue.has_powered_winch`	boolean	true \| false	Powered retrieval required for entries > 20–25 ft; manual too slow for IDLH deep extraction
`rescue.required_leg_clearance_ft`	decimal	3.0 (tripod typical)	Tripod-specific — minimum clearance needed on each of 3 sides for stable leg placement
`rescue.osha_1910_146_compliant`	boolean	true \| false	Confirms retrieval system meets OSHA 1910.146(k) non-entry rescue requirements
`rescue.has_auto_braking`	boolean	true \| false	Automatic brake prevents free descent of incapacitated entrant during controlled lowering or system failure

Frequently Asked Questions

Can a standard SRL (self-retracting lifeline) serve as the confined space retrieval system?

Standard SRLs (ANSI Z359.14 Type 1 or Type 2) are fall arrest devices designed to arrest free falls — they lock under sudden downward acceleration. They are not designed for controlled extraction of an incapacitated entrant. When a rescuer manually pulls on an SRL cable to raise an entrant, the SRL lock mechanism may engage and resist upward extraction because the device interprets the mechanical tension as a fall arrest event. Additionally, SRLs do not provide the controlled mechanical advantage needed to extract a 250-lb entrant from a 40-foot-deep tank. Some manufacturers make SRL-style retrieval/rescue SRLs (labeled as retrieval SRLs or RSLs) that allow both fall arrest during descent and controlled extraction during rescue — these have a separate extraction function. Encode rescue.is_man_rated = true only for retrieval SRLs explicitly designed for personnel extraction (such as the DBI-SALA Nano-Lok retrieval SRL), not standard fall arrest SRLs.

Does OSHA require the attendant to operate the tripod/davit retrieval system alone?

OSHA 1910.146 specifies that the attendant must remain outside the permit space during entry — they may not enter. However, OSHA does not prohibit additional personnel from assisting with retrieval from outside the space. For deep entries or heavy entrants, it is entirely appropriate (and may be physically necessary) to have multiple people operating a manual winch or assisting with the extraction. What OSHA prohibits is entry by the attendant for rescue purposes — the attendant must summon the pre-arranged rescue service if non-entry retrieval fails. This is why the employer's permit-required confined space program must pre-designate rescue services and ensure they can respond within a time frame appropriate to the hazard. The attendant's job is communication, monitoring, and initiating retrieval — not solo entry rescue.

What harness must the entrant wear for non-entry retrieval to work?

For non-entry retrieval to be effective, the entrant must wear a retrieval/rescue harness — not just a standard fall arrest harness. The retrieval harness must have a retrieval attachment point (typically a dorsal ring or a dedicated chest retrieval ring specified by the equipment manufacturer) that allows the entrant to be extracted in an upright position without their head dropping forward in a way that obstructs the airway or makes extraction through a narrow opening impossible. The Chest Seat Harness (Type X or Type M per ANSI Z359.11 classification) is commonly used for confined space entry because it maintains an upright orientation during retrieval and allows extraction through openings as small as 18 inches diameter. The entrant is NOT wearing a standard Class I or Class II harness in a confined space entry with retrieval lines — that geometry is wrong for vertical extraction. Encode harness.suitable_for_confined_space_retrieval = true for chest/seat harnesses with appropriate retrieval attachment points.

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