Water-trap holder is one of the internal ETCO2 module accessories, which produced by National medical. The user can fix this bracket on the monitors. During the installation, users just need to perforate the monitor outer casing with two 3mm diameter holes, and then screw self-tapping screws which is inside of the monitor through the outer casing to the holder.At the same time, users also need to perforate two 3mm diameter holes over the two screw holes to make the air tap of the holder go to inside of the monitor.It suggested that user can glue spreading around air tap which extending to inside of the monitor, which can make the holder fixed more firmly. The water-trap holder is supplied with the module sales. If it is damaged by customs occasionally, it can also be purchased separately.