Device for non-invasive ventilation (NIV), in particular at a continuous positive airway pressure (CPAP), comprising: - a gas admission module comprising an admission module body comprising: ▪ an internal gas passage , ▪ an oxygen injection port in fluidic communication with the internal gas passage , and ▪ a conduit connection end (101-1) with a gas supply port in fluidic communication with the internal gas passage , said conduit connection end (101-1) being configured for fluidically connecting a flexible conduit there, and - a ventilation module comprising a ventilation module body comprising: ▪ an upstream connection end (201-1) with a gas inlet port configured for fluidically connecting the flexible conduit there, ▪ a downstream connection end (201-2) with a gas outlet orifice configured for fluidically connecting a respiratory interface there, and ▪ an internal gas circuit fluidically connecting the gas inlet port to the gas outlet port , characterized in that the gas admission module and the ventilation module comprise coupling means (130, 201-2) allowing a user to releasably couple the ventilation module to the gas admission module , said coupling means (130, 201-2) comprising a blind-bottomed housing open to the outside and arranged in the admission module body of the gas admission module cooperating with the downstream connection end (201-2) of the ventilation module . - a gas admission module comprising an admission module body comprising: ▪ an internal gas passage , ▪ an oxygen injection port in fluidic communication with the internal gas passage , and ▪ a conduit connection end (101-1) with a gas supply port in fluidic communication with the internal gas passage , said conduit connection end (101-1) being configured for fluidically connecting a flexible conduit there, and ▪ an internal gas passage , ▪ an oxygen injection port in fluidic communication with the internal gas passage , and ▪ a conduit connection end (101-1) with a gas supply port in fluidic communication with the internal gas passage , said conduit connection end (101-1) being configured for fluidically connecting a flexible conduit there, and - a ventilation module comprising a ventilation module body comprising: ▪ an upstream connection end (201-1) with a gas inlet port configured for fluidically connecting the flexible conduit there, ▪ a downstream connection end (201-2) with a gas outlet orifice configured for fluidically connecting a respiratory interface there, and ▪ an internal gas circuit fluidically connecting the gas inlet port to the gas outlet port , characterized in that the gas admission module and the ventilation module comprise coupling means (130, 201-2) allowing a user to releasably couple the ventilation module to the gas admission module , said coupling means (130, 201-2) comprising a blind-bottomed housing open to the outside and arranged in the admission module body of the gas admission module cooperating with the downstream connection end (201-2) of the ventilation module . ▪ an upstream connection end (201-1) with a gas inlet port configured for fluidically connecting the flexible conduit there, ▪ a downstream connection end (201-2) with a gas outlet orifice configured for fluidically connecting a respiratory interface there, and ▪ an internal gas circuit fluidically connecting the gas inlet port to the gas outlet port , characterized in that the gas admission module and the ventilation module comprise coupling means (130, 201-2) allowing a user to releasably couple the ventilation module to the gas admission module , said coupling means (130, 201-2) comprising a blind-bottomed housing open to the outside and arranged in the admission module body of the gas admission module cooperating with the downstream connection end (201-2) of the ventilation module . <EOS>