An important blast injury mechanism is the rupture of the lungs and the gastrointestinal tract. In explosives safety studies and threat analysis the empirical model of Bowen is often used to quantify this mechanism. The original model predicts the lethality for a person in front of a reflecting surface caused by simple Friedlander blast waves. Bowen extended the applicability to persons in prone position and standing in the free field by making assumptions about the pressure dose at these positions. Based on new experimental data, some authors recently concluded that the lethality for a person standing in the free field is the same as for a person in front of a reflecting surface, contrary to Bowen's assumptions.In this article, we show that only for a short duration blast wave, the load on a person standing in the free field is comparable to that on a person in front of a reflecting surface. For long positive phase durations, a safe and conservative assumption is that the load on a person standing in the free field is the sum of the side-on overpressure and the dynamic pressure. This hypothesis is supported by common knowledge about blast waves and is illustrated with numerical blast simulations.In a step by step derivation we present a new standard for the prediction of lethality caused by Friedlander blast waves, which will be included in the NATO Explosives Safety Manual AASTP-4. The result is a comprehensive engineering model that can be easily applied in calculations. © 2016 Elsevier Ltd.