What device includes a small fan to assist with air circulation into the mask?

The correct answer is the powered air-purifying respirator (PAPR), which is specifically designed to enhance air circulation for the user. PAPRs use a battery-powered fan to draw in ambient air, which then passes through filters before being delivered to a hood or mask worn by the user. This active air circulation not only helps in providing a supply of filtered air, but it also makes it easier to breathe, especially in environments where air quality is compromised. The fan can be particularly beneficial in reducing heat buildup inside the mask, improving comfort during extended use.

Other options do not include a fan for air circulation. For instance, a supplied-air respirator (SAR) relies on an external source of air and does not utilize a fan; it provides clean air through a connected hose directly from a tank or compressor. An air-purifying respirator (APR) operates by filtering out contaminants from the air but does not have any mechanical assistance to enhance airflow. An open-circuit breathing apparatus typically involves supplying compressed air directly from a tank and does not include fan-assisted circulation. Thus, the defining feature of a PAPR is its powered system for air delivery and circulation, making it the correct choice.