[en] The present invention relates to a safety device such as an impact or crash cushion, in particular for a motor vehicle, with an elastic membrane 1â (1, figure 1), which partially or completely delimits a hollow space, which is filled by an inflation gas during an accident subject to elastic expansion of the membrane. The membrane is covered by a separate envelope 2, 3.1 in a gas-tight manner, said envelope being caused to open through the expansion of the membrane. In addition a catalyst 5 for the removal and/or an overlaying active substance for the active overlaying of an active substance escaping from the membrane may be arranged in the membrane and/or adjacent to the latter. The envelope may be flexible 2 or rigid 3.1. The membrane may comprise a synthetic or natural rubber, where the envelope is intended to prevent any active substances, such as aromatic substances giving rise to an odour, which are escaping from the elastic membrane from causing a nuisance to a person in proximity to the safety device.