Understanding the hazards of fire ground contaminants in aircraft accident investigation

The health risks from exposure to fire ground contaminants for firefighters are now generally accepted, but within the wider response community this awareness remains low. The Air Accidents Investigation Branch (AAIB) recognise the hazards that exposure to fire ground contaminants pose to its investigation teams and is continually evaluating these risks.

The AAIB is tasked with investigating accidents and serious incidents involving civil aviation within the UK (including UK Overseas Territories and Crown Dependencies). It is not uncommon for investigation teams to attend accidents where the subject aircraft has been involved in a fire and therefore potentially be exposed to the contaminants released because of combustion such as Ultrafine Particulates (UFP’s) and Volatile Organic Compounds (VOCs).

Evolving approach to dealing with contaminants

After attending the Invisible Risk Conference held at Cranfield in November 2022, the AAIB formulated an action plan to look at the emerging risk profile associated with UFP/VOC exposure.

Due to the range of hazardous materials likely to be present at an aircraft accident site, the AAIB has developed stringent Personal Protection Equipment (PPE) protocols refined over many years.

During AAIB investigation activities, it is not uncommon for our PPE to become contaminated with the products of combustion. An example would be our rescue jackets and trousers which, if the contamination is not removed, can be absorbed into the material and eventually permeate into the body via skin contact.

Another consideration is that AAIB teams can be deployed to multiple incidents within a short timeframe, therefore a ‘quick’ turnaround, often involving a small number of garments, is required to ensure clean PPE is readily available.

The PPE laundry provision within the AAIB was reviewed with options of in-house laundering or external suppliers considered.  After due consideration, the AAIB selected a new supplier who was able to offer an improved service tailored for our needs for no additional cost.

Another area for consideration is the use of Respiratory Protective equipment (RPE). When dealing with aircraft incidents where the release of particulates is of concern, it is mandatory for staff to wear either a fit -tested half mask respirator with a P3 particle filter or use a powered respirator.

Within the last twelve months the AAIB has purchased new powered respirators which are lighter and more comfortable than the previous respirators. Comfort is an important consideration because our inspectors often wear respirators for long periods of time. The masks supplied with these new respirators are considered consumables and are disposed after use, thereby eliminating the necessity of cleaning which can be problematic. It is important to note that the new respirators offer an assigned protection factor of 40.

Investing in research

Going forward, the AAIB in conjunction with the Institute of Naval Medicine (INM), intends to commence a series of studies into UFP and VOC release at aircraft accident sites. This study will also include burnt wreckage stored in the AAIB hangar facilities as part of the investigation process. A major difference in the AAIB’s exposure profile in comparison to a fire fighter, is that aircraft accident scenes are classed as ‘cold’ rather than ‘hot’.

Operating within a ‘cold scene’ it is understood that UFP’s and VOCs can be released for a significant period after the initial fire has been extinguished, although there is currently limited quantifiable data available as to the extent. The AAIB intends to gather sufficient data, to reassess the risk profiles and asks:

1. Does current PPE offer adequate protection?
2. How can further staff exposure be limited?
3. Can wreckage handling and storage processes be improved to limit further exposure?

The AAIB hope to commence this study in 2024 and an important aspect will be to share the findings with the wider responder community. The aspiration being to increase our knowledge relating to UFP/VOC release from ‘cold scenes’.

From the knowledge gained all organisations will be better placed to make decisions on the necessary steps required to further minimise exposure of all responders to fire ground contaminants.

For insights from the Invisible Risk conference, read our recent article Nine ways to reduce risk from contaminated PPE.