Rescue preparation before a nitrogen emergency
How can external alarm raising, entry control and rescue arrangements be prepared before a confined-space emergency?
30-second summary
When a person collapses in a confined space, a rescuer breathing the same atmosphere can also become a casualty. Raise the alarm and prevent entry from outside, while prepared rescuers use appropriate protection. Courage after an emergency cannot replace rescue arrangements made before work.
In manure-pit incidents investigated by NIOSH, relatives and coworkers died after entering to help a collapsed person. Assess both oxygen deficiency and toxic gases. An ordinary filtering respirator cannot supply missing oxygen; the rescue plan must fit the space, substances and access.
Work background and incident sequence
In a NIOSH case on 26 June 1989, a farmer entered a manure pit to clear a pump intake and collapsed. His brother entered in an attempted rescue and also collapsed. A family member later discovered them and called the fire service, but both died. An unplanned rescue compounded the original maintenance emergency.
On 26 July 1989, a worker entered a pit to replace an agitator-shaft component and collapsed while trying to leave. Relatives entered successively and five people died. Another would-be rescuer collapsed but was pulled out by an assistant and survived. Failure to emerge must trigger the planned response, not another unprotected entry.
Agitation can rapidly release gases produced by decomposition. Conditions before work may not persist during the task. Cleaning, mixing, draining and opening pipes alter residues and ingress. Planning must therefore consider how the work changes the atmosphere, not just an initial test.
At FFG in 2021, employees approached an oxygen-deficient freezer room to investigate or rescue colleagues after a nitrogen overflow. A manure pit and a freezer room differ, but both exposed people approaching others without recognizing the atmosphere. A warning limited to tank entrances does not address every hazardous room or pit.
Equipment and work principles
Adequate oxygen and absence of toxic substances are separate questions. Nitrogen displaces oxygen, while decomposition gases may also be toxic or flammable. A normal oxygen display does not exclude every contaminant, and a toxic sensor does not measure oxygen. Match sensor capability to substances present or generated.
HSE places avoidance of entry first, for example inspection by remote camera or sampling and cleaning from outside. That decision precedes adding rescuers. Where entry remains necessary, establish a system covering isolation, ventilation, testing, attendance and rescue arrangements.
Isolate material ingress through pipework and unintended machinery movement. HSE calls for verification that isolation is effective. Check connected lines, bypasses and drives, and communicate the isolation state so adjacent operation does not undermine the permit conditions.
Ventilation must deliver fresh air to the work location without recirculating contaminated exhaust. Continued generation or ingress requires suitable ventilation and monitoring during work. Do not add oxygen to improve the atmosphere; HSE warns that this greatly increases fire and explosion risk.
A small entrance can obstruct a rescuer wearing equipment, and an unconscious person cannot climb a ladder. Assess access and emergency extraction with the required protective equipment. Connect lifelines to an outside point and evaluate the actual route, including edges, pipes and obstructions.
Respiratory protection and casualty retrieval equipment perform different functions. Retrieval equipment does not protect a rescuer’s breathing, while breathing apparatus does not create an extraction route. Drills should connect communication, movement, retrieval and handover, using the actual access constraints.
Emergency communication must also work at night and across shifts. HSE guidance calls for arrangements specifying who receives an alarm and responds, including nights and weekends. Test the connection from the attendant to the rescue team as well as communication with the entrant. Possession of a phone alone does not establish a working link where reception is unavailable.
Check the opening before selecting rescue equipment. HSE guidance addresses access for a rescuer wearing respiratory protection and the possible need for lifting arrangements. An opening barely large enough for a person may not admit breathing apparatus and retrieval equipment together. Plan a route for extracting a collapsed entrant without snagging on obstructions.
Figure 2 highlights the checks described here.
- 1 Stop approachStop approaching so colleagues attempting rescue stay outside the hazardous atmosphere.
- 2 Call from outsideCall from outside and tell rescuers the location and hazards.
- 3 Control entryControl entry to prevent unprepared people from following inside.
- 4 Check rescue arrangementsCheck rescue equipment and procedure arrangements before emergency response.
Published chronology and investigation findings
HSE includes nights, shifts, weekends and closed premises in emergency communications. Define who receives the alarm and how responders learn the hazards. A successful daytime call does not test the arrangements for every working period.
The attendant monitors from outside and initiates the response. Lost communication should activate alarm, entry control and prepared rescue resources. Brief replacement workers and contractors, and do not assign one person simultaneous entry and outside attendance.
| When | Established account | Source |
|---|---|---|
| 1989-06-26 | Pump blockage entry followed by rescue entry; two deaths | NIOSH 90-103 Case 1 |
| 1989-07-26 | Agitator maintenance followed by successive rescue entries; five deaths | NIOSH 90-103 Case 2 |
| 2021-01-28 | Six employee deaths during FFG release and response | CSB FFG pp.7–8 |
| Planning | Avoid entry where possible; use a safe system where unavoidable | HSE INDG258 p.3 |
| Before work | Prepare emergency equipment, communication and drills | HSE pp.5–6 |
Consequences and emergency response
The shared failure was unprepared entry after seeing a collapsed person. A brief intended stay does not delay atmospheric effects. Call from safety and prevent further entry. Provide location, substances, measurements, isolation and access information without re-entering to obtain it.
First aid follows safe rescue. HSE calls for trained rescuers and first aiders with equipment they can use. Site planning should prevent additional exposure while responders are on their way and provide the equipment and substance information they need on arrival.
Questions for your site
| Question | How to check |
|---|---|
| Can the task be done without entry? | Compare remote inspection, sampling and cleaning options. |
| Who remains outside if contact is lost? | Assign and test attendance, alarm, control and rescue functions. |
| Can required protection pass through the entrance? | Evaluate access and retrieval equipment together during drills. |
| What can change the atmosphere during work? | Include mixing, cleaning and connected supplies in testing and ventilation plans. |
Application at Korean sites
Comparable work in Korea is subject to the Rules on Occupational Safety and Health Standards, MOEL Ordinance No. 450, effective 2026-03-02. The following concerns present work; findings about the incident depend on its investigation and proceedings.
Article 619 requires a confined-space program covering locations, hazards, pre-entry checks and training. Before work, establish personnel, measurements and corrective actions, possible gas ingress or generation, protective equipment and emergency contacts. Post the information at the entrance until work ends. Include gas arriving through connected supplies.
Article 623 places the attendant outside the confined space with continuous communication. When a worker is in distress, promptly notify the local fire service, take appropriate action with its assistance and immediately inform the employer and supervisor. An attendant entering the space also removes the outside alarm and control function.
Article 625 requires equipment for emergency escape and rescue, including breathing apparatus or supplied-air masks, ladders and ropes as appropriate. Check whether the equipment can actually be used through the entrance and along the extraction route. Rescuers must be protected from the atmosphere that caused the emergency; unprotected entry is not a rescue plan.
Article 640 requires drills at least once every six months on communications, rescue equipment, breathing apparatus or supplied-air masks and first aid, with retained records. The Article 626 continuous-ventilation exception has specified conditions, including 24-hour operation, and excludes certain spaces. Simply providing a portable fan does not establish the exception.