The best replacement for oxygen is altitude.

The best alternatives to oxygen are rated as following:

★★★★★	altitude
★★★★	nitrogen
★★★	air
★★★	carbon dioxide
★★	axiom
★★	ozone
★	o2
★	xmlspy
★	cpap
★	sulfur
★	hydrogen
★	sulfur more electronegative
★	chlorine more electronegative
★	oxygen concentrator
★	nitrogen heavier
★	gas oxygen
★	concentrator
★	nitrogen more electronegative
★	helium
★	water temperature
★	carbon monoxide
★	keystation
★	carbon dioxide heavier
★	nitrogen weight
	oxygen
	medical air
	welding oxygen
	compressed oxygen
	phlogiston
	launchkey
	oxide
	compressed air
	boiling hydrogen
	industrial oxygen
	oxygen concentrators
	sulfur better nucleophile
	salinity
	gaseous oxygen
	oxygen gas
	cyanogenmod
	nitrogen electronegativity
	nitrogen bonding
	partial pressure

Your alternative for oxygen is not listed? Suggest!

Speaking about oxygen, one probably shouldn't forget about cpap.

Other search terms related to oxygen and their ratings are:

★★★★★	cpap
★★★★★	copd
★★	humidification
★	everest
★	exercise
★	tracheostomy
★	copd patients
★	which science cannot breathe
★	bipap
	breathing
	respiration
	water
	thushara
	food to release energy
	oxygen
	emphysema
	cpap machine
	thushara subasinghe
	humidity

You have in mind a companion for oxygen and it is not yet here? Propose!

Scale is based on the average worldwide traffic of oxygen in all years. Click on graph for more.

oxygen

altitude

nitrogen