Mercury spill forces closure of Air Corps hangar at Baldonnel airbase

The spill occurred in the same hangar that recently hosted the Aviation and Aerospace Careers Expo, AvCon 2025. File picture: Sasko Lazarov/© RollingNews.ie

A toxic mercury spill temporarily shut down one of the Air Corps’ hangars, the Defence Forces have confirmed.

Details of the spill first emerged in an email sent on Monday by a commandant at Air Corps Headquarters in Casement Airbase, Baldonnel. He warned “all personnel” that Hangar No 4 was closed “due to a mercury spillage.”

He informed staff that the Air Corps Health and Safety Section had taken control of the clean-up operation and that the area would remain cordoned off until specialised cleaning equipment arrived.

A Defence Forces spokesperson confirmed the incident occurred at approximately 1.45pm on Monday.

A small quantity — 100 mg — of metallic mercury was accidentally spilled inside the hangar when an avionics device, a manometer, was dropped during transport.

The spokesperson said: “No personnel were exposed, and the affected area was immediately sealed off as a precautionary measure.

“Specialist mercury spillage cleaning kits were required, and all safety precautions were followed in accordance with mercury spillage guidelines.

“The Air Corps does not store metallic mercury as waste.

“In this case, the mercury was contained within a functioning avionics component, meaning no waste storage licence was required.” 

Air Corps Headquarters contacted the Health and Safety Authority (HSA) and notified the Environmental Protection Agency (EPA).

The spokesperson added: “There was no risk to personnel health at any time prior to the incident, as the mercury was securely contained and only present in a very small amount.

“The Air Corps remains committed to maintaining the highest standards of safety and environmental responsibility."

The use of mercury in aviation has largely been phased out because of its corrosive reaction with aluminium, the primary material used in modern aircraft construction.

It is considered so toxic to humans and planes that even mercury thermometers are banned on all flights.

If a thermometer were to break mid-flight, the mercury could corrode aluminium and potentially compromise aircraft safety. In addition, inhaled mercury vapour can cause severe neurological damage.

According to the Environmental Protection Agency (EPA), which enforces strict EU regulations on the transport and storage of mercury, the metal is “highly toxic,” and even minimal exposure can cause serious health effects.

The EPA also noted that mercury use is heavily restricted worldwide under the Minamata Convention, with even stricter regulations in Europe.

The spill occurred in the same hangar that recently hosted the Aviation and Aerospace Careers Expo, AvCon 2025.

The annual event showcases aviation careers and technology to more than 8,000 students across primary, secondary, and third-level education.

The Irish Examiner has learned that before the conference, the HSA received a complaint about the storage of turbine engine oils and hydraulic fluids in the hangar.

The Air Corps has been asked why the HSA visited the base and what actions or assurances resulted from the inspection.