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Glazing: the vulnerable link during an explosion
During an explosive event—an attack, an accidental explosion or an industrial overpressure event—glazing is the most vulnerable part of a building envelope. FEMA Guide 428 (Primer for Design of Commercial Buildings to Mitigate Terrorist Attacks, Risk Management Series) states this explicitly: lacerations caused by flying glass fragments are a major source of injuries during explosions. This is where blast-mitigation safety film—referred to as blast mitigation film in international technical literature—comes in. Installed on existing glazing, it retains broken glass fragments, but its role and limitations must be clearly defined before it is specified.
What the film does—and does not do
Safety film is a multilayer polyester (PET) substrate bonded to the inside face of the glazing with a high-performance adhesive. In an explosion, the glass will inevitably fracture. The film then acts as a containment membrane: its adhesive holds the fragments against the substrate, limiting their projection into occupied areas.
Glass-fragment retention is the only function that can be certified for a film in this context. It is important to clearly establish what the film does not do:
- it does not withstand the blast wave itself;
- it does not mechanically increase the glazing's resistance to pressure;
- it does not replace laminated safety glass or bullet-resistant glazing;
- it does not guarantee occupant protection in a severe or nearby event.
Compared with complete glazing replacement, film offers a lower intervention cost and can be removed without damaging the substrate. These benefits remain subject to the site's risk assessment and the nature of the threat; they do not, by themselves, guarantee performance.
Standards and guidelines: scope and limits of application
FEMA 428 recommends applying retention films to glazing in buildings exposed to blast risk as part of an overall damage-reduction strategy. These recommendations rely on specific threat assumptions—device type, estimated charge and regulatory context—and are not a universal requirement that applies independently of the exposure scenario.
In Europe, EN 13541 (Glass in building—Explosion-resistant security glazing) classifies glazed systems from ER1 (low overpressures) to ER4 (reinforced laminated glazing). Solar Screen's Clear 17 C is 485 µm thick, consists of four 100 µm polyester layers and is certified EN 13541 ER1 (source: official product sheet, solarscreen.eu/fr/products/clear-17-c). This level is suited to common architectural applications exposed to low overpressures.
In the United States, GSA TS01-2003 (Standard Test Method for Glazing and Window Systems Subject to Dynamic Overpressure Loadings) and ASTM F1642 define test protocols and classification levels for glazed systems exposed to blast loads. These references apply according to the regulatory framework of the relevant territory and do not constitute universal requirements.
[Image suggestion: comparative diagram of EN 13541 levels (ER1 to ER4)—Caption: EN 13541 certification levels for explosion-resistant glazing]
Critical variables: anchorage, framing and stand-off distance
The performance of blast-mitigation film depends on factors beyond the product selection itself.
Perimeter anchorage—referred to as an attachment system in US and UK guidance—is a mechanical fixing device that connects the film's edge to the frame of the window system. It is the most critical parameter. Without this connection, the film may be pulled away during an event, taking the broken glazing with it. The system transfers loads to the wall structure, significantly increasing the assembly's retention capacity. FEMA and GSA guidance recommends assessing frame-to-anchorage compatibility before specifying a solution.
Stand-off distance—the distance between the explosive source and the building—directly determines the intensity of the impulse pressure. The shorter this distance, the higher the pressures and the less adequate a film-only solution becomes.
Overall façade design—including frame profiles, glass-to-frame joints and the stiffness of the supporting wall—determines whether the assembly withstands the overpressure load or whether the construction system fails before the film. Assessing the product alone is not enough to qualify a complete system.
Decision criteria and professional validation
Before specifying a solution, several variables must be assessed by a security engineer or specialist design office: threat level, glass-to-film compatibility (particularly for low-emissivity, or Low-E, assemblies) and curing time. The PS adhesive used in Solar Screen films cures against the glass over 30 days (source: solarscreen.eu product sheets); the film reaches its nominal retention performance only after this period.
Installation quality is also critical. Incorrect installation of safety film on glazing—insufficient anchorage, poorly prepared surfaces or inadequate squeegee pressure—compromises the system's mechanical properties, regardless of the product's certification.
For commercial, public or school buildings exposed to a moderate threat level, EN 13541-certified blast-mitigation film provides a proportionate technical response. Solar Screen offers a range of certified anti-burglary and blast-mitigation safety films for different performance requirements. At high-risk sites—embassies, command centres and critical infrastructure—the film forms part of a broader system combining reinforced laminated glazing, blast-resistant curtains and an appropriate stand-off distance. In every case, a qualified professional must validate the installation decision using the standards applicable in the relevant territory and certified test results for the selected product.