Low-Order Deflagration: The Proven Method for Quieter, Safer UXO Disposal

First published 17 December 2024 · Updated 3 November 2026

Low-order deflagration is a way of disposing of unexploded ordnance (UXO) by burning out its explosive fill instead of detonating it. A small shaped charge pierces the casing and ignites the contents, which burn rather than explode. Underwater, that makes disposal around 15 to 20 dB quieter than a conventional high-order detonation, leaves no seabed crater, and typically keeps the debris within a few metres.

Since January 2025, UK regulators have expected low-noise methods like this to be the default for commercial offshore UXO clearance, with high-order detonation the last resort. This guide explains how deflagration works, what the research shows, where its limits are, and how Alford’s shaped charges are used on land and at sea.

Key terms

• High-order detonation: a donor charge sets off the full explosive content of the UXO.
• Low-order deflagration: the UXO’s fill burns at subsonic speed without detonating.
• NEQ: net explosive quantity, the mass of explosive in an item or charge.
• SPLpeak and SEL: peak sound pressure level and sound exposure level, the two noise measures regulators use to assess risk to marine mammals.
• Jet-forming cone (JFC): the liner in a shaped charge that forms the penetrating jet. For low-order work, it is magnesium.
• Joint Position Statement (JPS): the UK government statement on marine UXO clearance, published in January 2025.

How low-order deflagration works

1. Penetrate the casing. The operator places a shaped charge against the UXO at a set stand-off. Its magnesium cone forms a jet that pierces the casing without enough shock to trigger detonation.
2. Ignite the fill. The jet ignites as it forms and enters the explosive fill, starting a burn that travels slower than sound. A detonation, by contrast, travels through the explosive as a supersonic shock wave.
3. Burn out. The fill burns, gas pressure builds, and the casing usually splits open. No large blast wave and no crater. Remains typically stay close to the target for recovery.

Because the noise comes from the small shaped charge rather than the UXO, you can predict it in advance from the charge size alone.

High-Order vs Low-Order: Key Differences

The evidence

Three independent studies, two peer-reviewed, underpin low-order deflagration at sea. All used Alford shaped charges.

Both peer-reviewed studies were funded through the UK government’s Offshore Energy Strategic Environmental Assessment programme. Read our summary of the Danish trial in Exploring Environmentally Safer UXO Disposal Methods.

Case study: Moray West offshore wind farm

In 2023, EODEX cleared all 82 UXO found on the Moray West site in the Outer Moray Firth using low-order deflagration with an Alford disposal tool. It was the first UK offshore wind project to use the technique for an entire clearance campaign.

• 82 items, seven types, from 6 kg projectiles to a 700 kg German Luftmine B sea mine.
• None high-ordered. 53 items (65%) were neutralised on the first attempt; the Luftmine B took four.
• 28 kg of explosive in total, against an estimated 830 to 2,075 kg for high-order clearance of the same items.
• No seabed craters at any clearance site, and all scrap recovered.
• Quieter than predicted. The highest measured peak level was 208.4 dB re 1 µPa at 1 km. For the Luftmine B, levels were 22 dB below the prediction for a high-order detonation.

UK regulation: the Joint Position Statement

The Joint Position Statement on marine UXO clearance, published on 21 January 2025 by Defra and the UK’s devolved governments and regulators, sets out three expectations for commercial developments:

• Low-noise methods should be the default for clearing any type of UXO.
• High-order detonation should be the last resort, allowed as a contingency only when the most appropriate low-noise method has failed after at least three attempts, all best practice has been applied, and the licensing authority has agreed in advance.
• Evidence decides preference. Tools backed by both controlled testing and at-sea clearances sit in the preferred category.

Low-order deflagration with Alford tools has both kinds of evidence. The statement does not cover military clearance, which is exempt from marine licensing.

The practical benefit is in licensing. Because noise depends on the small, known tool charge rather than an uncertain UXO NEQ, acoustic modelling and mitigation planning are simpler and less precautionary.

The limits

Low-order deflagration is the better method, not a perfect one:

• It may take more than one attempt. At Moray West, 35% of items needed a repeat.
• Residue must be recovered. Not all the explosive is always consumed. Preliminary samples from the Danish trial showed elevated explosive residues in sediment beside a low-order site, and ROV or diver recovery is part of the job.
• Not every item is a candidate. Severe degradation, depth or very thick casings can rule it out. The JPS recognises these as extraordinary circumstances.
• It is still loud. The shaped charge itself is an explosive event. Mitigation such as acoustic deterrents is still needed to protect harbour porpoises and other sensitive species.

On land, too

Low-order deflagration is not only a maritime technique. Vulcan achieves low-order results in more than 90% of EOD tasks. The same tool also works in a deliberate detonation role: in April 2026, a Vulcan neutralised a Second World War bomb at the Changi East construction site in Singapore. The Humanitarian Demining Vulcan brings the same approach to NGO clearance teams, and Magma scales up for the largest air-dropped bombs.

Alford’s low-order tools

• Vulcan: 10 to 50 g, user-filled, for land and underwater; used in the 2020 quarry study.
• Pluton: 250 to 300 g, with magnesium cones for low-order work; used in the Danish sea trial and a North Sea offshore clearance.
• Magma: 100 to 600 g for the heaviest munitions.
• PLMEOD Kit: Pluton packaged for underwater and waterline use.
• Project REDS: lets the ROVs you already operate deploy and fire these charges.

For how the jet forms and why magnesium matters, see Shaped Charges: How They Work. For the wider clearance picture, see UXO Clearance.

Frequently asked questions

What is low-order deflagration?

A UXO disposal method in which a small shaped charge pierces the casing and ignites the explosive fill, so it burns out instead of detonating.

How much quieter is it than high-order detonation?

Around 15 to 20 dB lower in sea trials, and typically more than 20 dB lower in controlled tests. The noise comes from the shaped charge, not the UXO.

Which shaped charges are used?

Alford’s Vulcan, Pluton and Magma, fitted with magnesium jet-forming cones. Copper cones are more likely to cause detonation, so they are not used when a low-order result is the aim.

Is it required under UK rules?

The January 2025 Joint Position Statement says low-noise methods should be the default for commercial offshore UXO clearance, and high-order detonation should be the last resort. Low-order deflagration is a low-noise method with both controlled and at-sea evidence.

Has it been used on an offshore wind farm?

Yes. At Moray West in 2023, 82 UXO from 6 kg to 700 kg NEQ were cleared by low-order deflagration, with none detonating and no seabed craters.

Does it leave anything behind?

Sometimes. Not all the explosive is always consumed, so casing and residue are recovered afterwards. They are typically found within a few metres of the target.

Who developed it?

Alford Technologies developed low-order deflagration with magnesium shaped charges; the design is covered by patent publication WO 03/058155 (2003). The UK’s National Physical Laboratory describes it as a method developed by Alford.

Talk to our EOD specialists

Whether you are planning an offshore clearance campaign or equipping an EOD team, our specialists can advise on tools, configurations and training. Contact us or see our EOD, IEDD and Maritime EOD training.

Related: Exploring Environmentally Safer UXO Disposal Methods · Shaped Charges · UXO Clearance · Magma v Tallboy