Council Regulation (EC) No 1099/2009 on the protection of animals at the time of killing lists in Annex I the stunning interventions currently allowed in the EU, together with the related conditions under which those interventions can be implemented. The regulation allows the Commission to amend Annex I, listing additional stunning interventions, provided they ensure a level of animal welare at least equivalent to that ensured by the one already approved. EFSA was requested to perform such assessment with regard to the implementation of the low atmospheric pressure stunning (LAPS) system on broiler chickens. The ad hoc Working Group (WG) set up by EFSA performed the assessment in three main steps, i.e. checking the data provided against the criteria laid down in the EFSA Guidance (EFSA AHAW Panel, 2013); running an extensive literature search, followed by data extraction and performing a judgemental ranking exercise based on expert opinion. As main outcome, the LAPS intervention was found to be able to provide a level of animal welfare not lower than that provided by at least one of the currently allowed methods. The overall assessment of EFSA is valid ONLY under the technical conditions described in the submission and for broiler chickens, intended for human consumption, weighting less than 4 kg. Deviations from these conditions might have different consequences for animal welfare which were not assessed in this exercise. The LAPS method may, in addition to commercial slaughter, be suitable for depopulation, respecting the technical conditions defined in the present conclusions. The WG considers that a revision of the present version of the EFSA Guidance could be beneficial.