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Blast Overpressure (BOP)—also referred to as overpressure or high-energy impulse noise—is the pressure produced by a shock wave that exceeds normal atmospheric pressure. Shock waves may result from explosions or sonic booms. BOP is a damaging consequence of explosive detonations and weapons fire. Exposure to these shock waves can cause injury primarily to hollow organ systems such as the auditory, respiratory, and gastrointestinal systems,¹ but can also significantly affect fluid-filled organs such as the brain.
Overpressure in Enclosed Spaces
The harmful effects of overpressure are most pronounced in enclosed environments, where pressure cannot easily dissipate. Under such conditions, the impact is magnified, partially mitigated only by structural dissipation, and the duration of exposure is extended.
Overpressure in an enclosed space can be estimated using Weibull’s formula:
Δp=(m/V)0.72Δp=(m/V)0.72
where:
- 2410 is a constant based on 1 bar (100 kPa; 15 psi)
- m = net explosive mass, calculated using all explosive materials and their relative effectiveness
- V = volume of the enclosed space
The visible and invisible impacts of blast.
The above table, based on Department of Defense (DoD) data from Glasstone and Dolan (1977)2. and Sartori (1983)3., summarizes the effects of increasing blast pressure on various structures and the human body. This data originates from weapons tests and blast studies to assess the effect of blast overpressure on structures and people.4.
The below graphs show the variation in pressure 'intensity' in an open air explosion as opposed to a closed-space. In short the open air rise quickly to peak and dissipates relatively quickly. The closed-space also rises quickly but the intensity is prolonged even causing 'rebound' type secondary impacts due to reflection, etc.
The Defense and Veterans Brain Injury Center (DVBIC) reports that more than 50% of injuries sustained by soldiers during the Iraq and Afghanistan conflicts were caused by explosive devices such as bombs, grenades, landmines, mortar and artillery shells, and improvised explosive devices (IEDs). Since 2006, blast-related trauma has been the leading cause of injury among U.S. and allied military personnel.
Blast-induced brain injuries can present in multiple forms, including cognitive impairment, behavioural changes, and emotional disturbances. They are frequently complicated by comorbid conditions such as depression, anxiety, and post-traumatic stress disorder (PTSD).
At present, diagnosis relies largely on neurocognitive testing and advanced imaging techniques. More recently, the Department of Defense (DoD) has trialled the use of “body sensor” technology, in which soldiers wear devices that record overpressure exposure from blasts. However, these systems currently provide only semi-quantitative data, limiting their ability to accurately capture injury severity.
To address this gap, research groups such as GLIA are advancing specific and sensitive biomarker platforms designed to improve diagnostic accuracy. These biomarkers aim to support earlier detection, enhance triage, and guide clinical decision-making—ultimately helping to mitigate the long-term impact of undiagnosed or untreated traumatic brain injury (TBI).
In parallel, ongoing collaborations are exploring the integration of sensor-based technologies with biomarker assays to provide a more comprehensive assessment of injury burden. The goal is to enable real-time, actionable insights for clinicians both on the battlefield and in acute medical settings, improving immediate care and long-term recovery for injured soldiers.