Air flow sensor

A method comprising the steps of:

• providing a portable test device having an air flow sensor, a tubular member having a first end connected to the air flow sensor and a second end that extends beyond an outer surface of the housing, wherein the tubular member defines a passageway extending between the first end and the second end such that the first end is in fluid communication with atmosphere that surrounds the outer surface of the housing, wherein the tubular member is retractably connected to housing and sensor such that a majority portion of tubular member is contained within housing when the portable test device is not being used and can be extended therefrom beyond the outer surface of the housing and into a working position, wherein the tubular member is a flexible plastic tube;
• interfacing the portable test device with a working device having an exhaust passage, wherein the working device is a clothes dryer having:
• a door, a lint filter and a blower, wherein the interfacing step includes inserting the second end of the tubular member into a clothes drying area of the clothes dryer, upstream from the lint trap, the exhaust passage and the blower;
• closing the door of the clothes dryer such that the second end remains within the clothes drying area;
• activating the clothes dryer for arrangement in an on condition;
• comparing internal pressure within the clothes dryer against an environmental pressure outside of the clothes dryer to identify whether a sufficient vacuum is present within the clothes dryer;
• determining an output characteristic when the difference between the internal pressure and the environmental pressure is less than a pre-determined threshold;
• and
• providing the output characteristic, wherein the detection occurs without modification of the dryer, wherein the tubular member is adapted to extend through the door when arranged in a closed orientation without materially affecting the operation of the clothes dryer.