Introduction:

Escape, Evacuation and Rescue Analysis (EERA) is a detailed engineering study that evaluates the feasibility and reliability of the provisions for personnel to escape from a hazard, evacuate to a place of safety, and be rescued if necessary during a major accident emergency. It is a key requirement for safety cases under regulations like COMAH (Seveso III). EERA examines the entire timeline from alarm to safe haven.

Purpose:

The purpose of EERA is to ensure that personnel have a high probability of surviving a major accident. It aims to: 

1) Verify that escape routes are available, accessible, and protected for a sufficient time (Tenability Analysis) during a developing incident, 

2) Confirm that the evacuation process (including muster and headcount) can be completed within the Available Safe Egress Time (ASET), and 

3) Ensure that rescue and medical assistance for incapacitated persons is possible. It challenges assumptions about human performance under extreme stress.

Methodology:

EERA is a scenario-based, time-dependent analysis:

1.  Define Accident Scenarios: Select relevant major accident scenarios from the QRA/PHA (e.g., large jet fire, toxic cloud release, explosion).

2.  Determine Hazard Development Timeline (ASET): Using consequence models, determine how the hazard (heat, smoke, toxicity, overpressure) escalates over time and geography. This defines the "clock" for response.

3.  Evaluate Escape & Evacuation Timeline (Required Safe Egress Time - RSET): Model the human response timeline:

    Detection & Alarm Time: Time for the event to be detected and alarms sounded.

    Recognition & Response Time: Time for personnel to recognize the alarm and initiate escape.

    Travel Time: Time to move along escape routes to the muster point or safe refuge, considering impediments (obstacles, congestion, impaired visibility).

4.  Compare ASET vs. RSET: For each scenario and personnel location, verify that RSET < ASET, with a safety margin. Evaluate the survivalbility of escape routes and muster points.

5.  Assess Rescue Capability: Review the provisions for locating, extracting, and treating casualties within the hazardous environment.

6.  Recommend Improvements: If gaps are found, recommend measures such as additional escape routes, protected refuges, improved alarm systems, signage, training, or changes to muster points.

Importance in the Process Industry:

Technical safety systems are designed to prevent incidents, but EERA acknowledges that failures can still occur and focuses on saving lives when they do. It is a critical, human-centered analysis that ensures the facility design supports survival. It prevents situations where personnel have theoretically "safe" egress routes that are actually impassable within the time before being overcome by heat or toxins. For COMAH sites, a robust EERA is mandatory to demonstrate that consequences to people have been mitigated. It directly informs emergency drills, training, and the design of temporary safe refuges.