The use of combustible sandwich panels in industrial and commercial buildings continues to generate debate within the fire engineering community, says ASP Fire CEO Michael van Niekerk.

He notes that while these materials “undoubtedly present fire risks”, treating all combustible-core panels as inherently unsafe overlooks the more fundamental question on what causes fires and how those risks can be managed effectively.

A rational engineering assessment demonstrates that fire safety is determined not only by the materials used in construction, but by the interaction between ignition sources, building occupancy, fire load, operational practices and the effectiveness of active and passive fire protection systems.

“Fire engineering is fundamentally about managing risk. Combustible sandwich panels are one component within a much broader fire safety strategy,” says Van Niekerk.

A recently completed technical assessment by ASP Fire examines combustible sandwich panel construction from this perspective, evaluating both the performance characteristics of different core materials and the engineering controls available to reduce fire risks.

One of the report’s key findings is that combustible sandwich panels should not be considered in isolation from the buildings in which they are installed. Many buildings use sandwich panels as external cladding or as internal environmental enclosures, while the structural integrity of the building remains dependent on steel, reinforced concrete or masonry.

Consequently, the presence of combustible-core panels does not necessarily determine how a building performs during a fire. Instead, the report argues that ignition sources remain the primary concern.

Drawing on research published by the National Fire Protection Association, the assessment notes that electrical distribution equipment, lighting systems, power transfer infrastructure and process heating equipment continue to account for a significant proportion of industrial and manufacturing fires.

“By the time combustible sandwich panels become fully involved in a fire, flashover has often already occurred. At that stage the contents of the building are already contributing substantial heat release, regardless of the construction materials,” explains Van Niekerk

Material Selection is Important

The report acknowledges that not all combustible sandwich panel core materials perform equally under fire conditions. A key performance indicator is the Limiting Oxygen Index (LOI), which measures the minimum oxygen concentration required for a material to sustain combustion.

Materials with an LOI below about 24% can sustain combustion under normal atmospheric conditions, while higher-LOI materials are significantly less likely to propagate fire once an ignition source is removed.

The assessment compares several commonly used insulation cores, including expanded polystyrene (EPS), polyurethane (PU), polyisocyanurate (PIR), phenolic foam, mineral wool and vacuum insulated panels.

Fire-retardant EPS products with an LOI exceeding 24% differ substantially from conventional EPS, as they generally self-extinguish when external flame exposure ceases. PU and PIR systems provide improved thermal performance but remain combustible and can produce dense smoke and toxic combustion products under fire conditions.

Van Niekerk adds that mineral wool systems offer “excellent fire resistance” but are not universally suitable. He explains that in high-humidity or condensation-prone environments, fibrous insulation may create operational challenges associated with moisture retention and mould formation.

“There is no universally perfect insulation material. Every solution involves balancing fire performance, thermal efficiency, durability, operational suitability and commercial viability.”

Managing Ignition Sources

The report’s most significant conclusion is that reducing ignition risk frequently provides greater fire safety benefits than focusing exclusively on replacing combustible sandwich panels. Rather than advocating wholesale replacement programmes, the assessment recommends a layered risk mitigation strategy that addresses the most common causes of industrial fires.

Central to this approach is rigorous electrical risk management, including independent six-monthly electrical inspection and certification by master electricians, supported by quarterly thermal imaging of distribution boards and heavily loaded electrical circuits to identify developing faults before ignition occurs.

The report also recommends installing earth leakage protection, overload protection and arc fault detection devices where appropriate to reduce the likelihood of electrical failures.

Beyond electrical systems, the report advocates the use of early-warning fire detection linked to 24-hour monitoring centres, together with thermal closed-circuit television systems capable of identifying abnormal heat signatures before a fire develops.

The assessment further recommends improved compartmentalisation to limit fire spread, as well as engineered ember-trap systems for facilities that use direct solid-fuel heating, thereby preventing embers from igniting combustible materials within the building.

“Electrical failures remain one of the leading causes of industrial fires. Investing in proactive electrical monitoring often delivers greater risk reduction than replacing construction materials while leaving ignition hazards unchanged,” he notes.

Realistic Engineering Solutions

The report highlights the economic realities facing many industrial sectors. Industries operating on narrow margins may find wholesale replacement of existing combustible sandwich panels financially impractical.

Higher-performing alternatives such as PIR, mineral wool or vacuum insulated panels can cost substantially more than fire-retardant EPS systems, while some applications may require insulation characteristics that non-combustible products cannot readily provide.

Instead of prescribing a single solution for every application, the report recommends evaluating combustible materials as one component of the total fire load within a building.

Therefore, where combustible sandwich panels constitute only a small proportion of the overall combustible material present, and appropriate engineering controls are implemented, the residual risk may be reduced to an acceptable level.

“Good fire engineering is rarely about absolute positions. It is about understanding where the real risks lie, selecting the most appropriate engineering controls and implementing practical measures that protect both people and property. A rational, evidence-based approach enables informed decisions that improve fire safety without imposing unnecessary commercial burdens,” concludes Van Niekerk.