Why in news?

A preliminary report indicates that the Red Fort blast was carried out using Ammonium Nitrate Fuel Oil (ANFO) combined with a detonator, likely triggered manually. The explosion killed may people, occurring just hours after a major crackdown on a Jaish-e-Mohammed terror module.

The bomb was placed inside a white Hyundai i20 with Haryana plates, a vehicle that had been resold multiple times, including to a man from Pulwama, to mislead investigators.

What’s in Today’s Article?

• How Ammonium Nitrate Fuel Oil (ANFO) Triggers Powerful Explosions
• Legal Controls on Ammonium Nitrate in India

How Ammonium Nitrate Fuel Oil (ANFO) Triggers Powerful Explosions?

• Ammonium nitrate (NH₄NO₃) is a widely used fertilizer but also a strong oxidiser capable of causing intense, high-temperature explosions when combined with the right substances.
• On its own, ammonium nitrate cannot explode — it must be mixed with a volatile secondary material, such as fuel oil, and then triggered by an external detonation that generates extremely high heat.
  • However, if exposed to high temperatures or a strong shock, it can violently decompose and sometimes explode even without added fuel, as seen in several past industrial accidents.
• The mixture, known as ANFO (Ammonium Nitrate Fuel Oil), is easy and inexpensive to produce and is commonly used in mining and construction because it is stable, safe to store, and extremely powerful when properly detonated.
  • A typical ANFO charge is roughly 94% ammonium nitrate and 6% fuel oil; industrial-grade ammonium nitrate can be used to make such a mixture.
  • On its own it usually will not detonate unless exposed to very high heat or a detonator.
  • The stronger the initiating blast, the more intense the resulting explosion.
• How Investigators Confirm Ammonium Nitrate Use After a Blast?
  • Even after a blast site is washed, investigators can detect ammonium nitrate through residual particles left behind.
  • ANFO explosions release gases like nitrous oxide, carbon dioxide, and nitrogen, which disperse quickly.
  • But unburnt ammonium nitrate particles often settle on windows, vehicle parts, road surfaces, dust, or clothing.
  • Although washing removes some material, sensitive chromatographic tests can still identify trace amounts of the chemical on almost any surface, helping confirm its use in the explosion.
• How Investigators Identify If Fertilizer Was Converted Into an Explosive?
  • Ammonium nitrate used as fertilizer is generally safe, but it becomes dangerous if exposed to high heat or a strong shock, which can cause violent decomposition and even detonation.
  • To intentionally convert fertilizer into an explosive, fuel oil is added to create This combination still requires a detonator to trigger the blast.
  • Investigators can determine misuse by checking for:
    • Presence of fuel residues,
    • Signs of detonator components,
    • Chemical ratios matching ANFO,
    • Trace elements indicating industrial-grade ammonium nitrate.
  • These clues reveal whether ordinary fertilizer was transformed into a powerful explosive mixture.

Legal Controls on Ammonium Nitrate in India

• India strictly regulates the sale and possession of ammonium nitrate.
• Under rules introduced in 2012 and updated in 2021, any mixture containing over 45% ammonium nitrate is legally classified as an explosive.
• A District Magistrate may permit possession of up to 30 metric tonnes, while larger quantities need approval from Petroleum and Explosives Safety Organisation (PESO).
  • PESO issues licences for the manufacture, storage, transport, and use of large quantities of ammonium nitrate.
• Buyers must clearly state why they need the chemical, and all licensed transactions are tracked through the System for Explosive Tracking and Tracing (SETT).
• This means that its manufacture, storage, transport, and use require licences from the  PESO, and unauthorised individuals are prohibited from purchasing or possessing ANFO or related substances.
• Given these restrictions, a key question for investigators is how the terrorists obtained such large quantities of ammonium nitrate and other explosive materials used in the Red Fort blast.