We present a case where mechanical obstruction in the anaesthesia delivery system caused by plastic wrapping from a filter was misinterpreted as severe bronchospasm. The patient suffered severe hypoxia before the problem was solved by using a free-standing self-expanding ventilation bag. This near-fatal incident emphasises the importance of thorough equipment checking routines, rapid troubleshooting and how equipment failure may be misinterpreted as a medical complication. It also shows how transparent container material can become a medical hazard.