Hazard Tier Classification — NFPA 350 Rescue Response Modes
TIER I — LOW HAZARD
15:00
Clock starts on ARRIVAL
No recognized hazards, but could require technical rescue if an entrant becomes incapacitated (medical event, fall).
Fire department may be viable at this tier.
TIER II — MODERATE HAZARD
12:00
Clock starts at INCIDENT (includes drive time)
Non-life-threatening hazards requiring rapid intervention. Actual or potential hazards present. Complex extraction.
On-site capability likely required.
TIER III — HIGHEST HAZARD
2:00
Dedicated team. No other duties.
Life-threatening hazards — actual or potential IDLH. Immediate intervention capability required.
Dedicated on-site team. No other responsibilities.
If a confined space entrant became unconscious, is there anything else in the space that could harm them while they wait for rescue?
If the answer is yes — you are most likely working with a Tier III space.
Rescue Team Staffing — NFPA 350 Table A.10.9.1
NFPA 350 Table A.10.9.1 — Confined Space Rescue Team Staffing by Space Conditions| Space Conditions | Team | Composition |
|---|
| No obstructions/entanglements. Entrant on retrieval system. No atmospheric hazards. | 1 | 1 Non-Entry Rescuer |
| Obstructions present. Not on retrieval. No atmospheric hazards. No vertical extraction. | 3 | 1 Rescue Attendant, 2 Rescue Entrants |
| Obstructions. Not on retrieval. No atmospheric hazards. Vertical extraction required. | 5 | 1 Attendant, 2 System Operators, 2 Entrants |
| Obstructions. Not on retrieval. Atmospheric hazards (SCBA). No vertical extraction. | 5 | 1 Attendant, 2 SCBA Entrants, 2 Backup Entrants |
| Obstructions. Not on retrieval. Atmospheric hazards (SAR). No vertical extraction. | 6 | 1 Attendant, 2 Entrants, 2 Backup, 1 Air Supply Op. |
| Obstructions. Not on retrieval. Atmospheric hazards (SCBA). Vertical extraction. | 7 | 1 Attendant, 2 Operators, 2 Entrants, 2 Backup |
| Obstructions. Not on retrieval. Atmospheric hazards (SAR). Vertical extraction. | 8 | 1 Attendant, 2 Operators, 2 Entrants, 2 Backup, 1 Air Op. |
All tiers require technician-level training per NFPA 1670. The tier determines speed, not skill. Pre-incident planning validates team size for specific spaces.
Air Monitoring — The 4-Foot Rule
Both OSHA Appendix B and NFPA 350 §7.3.10 require atmospheric testing at 4 ft (1.2 m) intervals from the opening inward (horizontal) or top to bottom (vertical), and to each side. "Top, middle, bottom" is not sufficient — a 24-foot vertical space requires 7 sample points, not 3. Test in this order: oxygen, then flammable gases, then toxic contaminants.
OSHA Requirements for Rescue Service Evaluation
Evaluate Response Time
Evaluate the rescue service's ability to respond in a timely manner, considering the hazards identified.
1910.146(k)(1)(i)
Evaluate Proficiency
Evaluate proficiency with rescue-related tasks and equipment for the specific permit spaces identified.
1910.146(k)(1)(ii)
Inform of Hazards
Inform the rescue team of all hazards they may confront when called to perform rescue at the site.
1910.146(k)(1)(iv)
Provide Access for Practice
Provide the rescue service access to all permit spaces to develop rescue plans and practice operations.
1910.146(k)(1)(v)
Annual Practice Required: Rescue teams must practice permit space rescues at least once every 12 months using simulated operations in actual or representative permit spaces. Representative spaces must simulate the types of spaces from which rescue is to be performed in opening size, configuration, and accessibility. — 1910.146(k)(2)(iv)
Starting the Conversation — Questions for Each Party
Facility / Space Owner Should Ask
What is the rescue service's average response time to our location — and does it meet the tier requirement for our spaces?
Facility
How many qualified rescuers will respond, and does that number meet the NFPA 350 staffing table for our specific spaces?
Facility
Has the rescue team been to our site? Have they seen the actual spaces and practiced rescue operations in or around them?
Facility
Can the rescue service demonstrate a timed rescue in a representative space to verify their capability?
Fire Department / Rescue Service Should Ask
What are the specific hazards in each permit space — atmospheric, engulfment, entanglement, configuration?
Fire Dept / Rescue
What tier classification does each space require, and can we realistically meet that response time window?
Fire Dept / Rescue
Can we access the actual spaces to pre-plan, take measurements, and practice rescue operations before an emergency?
Fire Dept / Rescue
Are there spaces on this site for which we honestly cannot meet the tier requirements? If so, who fills that gap?
For third-party rescue contractors: These same questions apply. The facility should evaluate your response time, team size, training credentials, and familiarity with their specific spaces before signing an agreement — not after. OSHA requires this evaluation regardless of whether rescue is provided by a fire department, an in-house team, or a contractor.
Space Assessment — Complete for Each Permit Space
Space Identification
Tier Classification (I, II, or III)
Primary Hazards in This Space
Response Time Evaluation
NFPA 350 Response Time Required for This Tier
Rescue Service Actual Response Time
Does the Rescue Service Meet the Tier Requirement?
If No — Gap and Mitigation Plan
Team Size Evaluation
Min. Team Size from NFPA 350 Staffing Table
Actual Team Size Available from Rescue Service
Does the Available Team Meet the Minimum?
If No — Gap and Mitigation Plan
Rescue Service Information
Rescue Service Provider Name
Training Standard (NFPA 1006 / 1670 / Other)
Date of Last Practice / Drill
Rescue Readiness Checklist
Rescue service response time evaluated for this site
Rescue service proficiency evaluated for this space type
Rescue service informed of all known hazards at site
Rescue service given access to spaces for pre-planning
Rescue practice conducted within the last 12 months
Written agreement in place with rescue provider
Team size meets NFPA 350 staffing guidance for this space
Response time meets NFPA 350 tier requirement
Air monitoring at 4 ft intervals per OSHA App. B / NFPA 350
Backup plan for spaces where primary rescue can't meet tier
The goal is not to pass or fail. The goal is to discover the gaps now — before the emergency — and develop viable options. A known shortcoming with a plan is infinitely better than an unknown gap discovered during a rescue.