Background: Providing supplemental oxygen with a blow-by method is used to provide additional oxygen to patients who will not tolerate an oxygen delivery device in direct contact with their face. Blow-by methods are often improvised from parts of standard equipment. The performance is very dependent on the distance to the face and the direction of the gas flow. Blow-by methods are used by anesthetists during transport but their performance in delivering supplemental oxygen has only been tested in static situations. The aim of this nonclinical study was to determine the performance of different blow-by methods in the delivery of additional oxygen to pediatric patients during transport., Methods: A manikin of a child with a facemask of appropriate size was transported along a 60 m corridor from the operating theater to the PACU. Oxygen delivery to the face of the manikin was measured during transport. Six blow-by methods were tested with oxygen flows of 3, 6, and 10 L/min and with the facemask at 0 cm from the face and at 5 cm from the face. The outcome parameter was: blow-by method reaching and maintaining an FiO 2 >50% during transport from the pediatric operating theater to the PACU., Results: At 0 cm from the face, five out of six blow-by methods maintained a FiO 2 >50% with all three flow rates. At 5 cm only two of the blow-by methods were able to maintain an FiO 2 >50% and this only at flow rates of 10 L/min. All other blow-by methods provided lower FiO 2 s; in three, the FiO 2 decreased to values only marginally above 21%. The decrease in FiO 2 typically started within 6-12 m from the start of the transport., Conclusion: It is concluded that the ability of blow-by methods to deliver a FiO 2 >50% depends on the method used and distance from the face., (© 2018 The Authors Pediatric Anesthesia Published by John Wiley & Sons Ltd.)