An air filtration system and a helmet for use in the air filtration system are disclosed and utilized to filter air between a head and body of a user and an external environment. Combined use of ozone and chlorine exploits high oxidation potential of ozone while retaining longer lived residual effectiveness of chlorine for high efficacy against contaminants, particularly biological and organic. In an example, the apparatus may be embodied as a memory device controller including a flash translation layer. comprises an electrode or the like indicating sensor element embedded in the structure of the sleeve, or integrally forming a part thereof, having an area that covers the inner perimeter area of the sleeve by its major parts. Environmental sensors are used to make the determination more accurate. The on time may be adjusted by the amount of information to be displayed, the font size of the information, the behavioral characteristics of the end user, the type of viewing activity, and the like.