The behavior of gas flow in air has been demonstrated visually under gradient magnetic fields in the range 0-40 T/m under 0-1.5 T. The magnetic behavior depended on the concentration of oxygen. Pure oxygen or nitrogen mixed oxygen (> 30%) was observed to be attracted by a magnetic field and act like a magnetic fluid where the magnetic effect on the gas was comparable to that of normal diffusion. In contrast, nitrogen gas escaped from magnetic fields of high intensities, and no magnetic field effect was observed for the flow of air. These phenomena were explained by the difference between the force acting on the gas and that acting on the air surrounding it under gradient magnetic fields. The magnetic force increased with increasing concentration of oxygen. This explanation can be also applicable to the escape of flames from magnetic fields of relatively high intensity or the magnetic quenching of flames inside a pair of columnar poles.