A gas ventilation mask includes an anesthesia nasal mask and a mouth mask defining respectively a nasal chamber and an oral chamber, detachably connected to one another so that the nasal mask and the mouth mask may be used either separately as a nasal mask or as a mouth mask, or as a combination nasal-mouth mask. Also provided is a mask anchor for holding a face mask on a patient, includes a head support for engaging a back of a patient's head, a posterior head strap that originates from behind the patient's head, in contact with the patient's head and attaches either directly or indirectly to the mask when the mask is on the patient's face, wherein the strap can be tightened to create a seal to allow for positive pressure ventilation or left loose and for providing supplement oxygen. Also provided is an anesthesia mask strap system having a first expandable strap portion having the ability to extend； second and third non-expandable strap sections fixed to ends of the first expandable strap section； and an adhesion section for fixing a length of the strap system when the second and third non-expandable strap sections are pulled to tension the expandable strap section.
