Abstract: A hydrocarbon control system includes a base device, a field device, and a mobile device. The base device includes a key generator configured to generate a temporary key. The field device is configured to restrict or allow access based on verification of a received key. The mobile device is configured to communicate with the base device to receive the temporary key when in proximity of the base device, communicate with the field device to provide the temporary key to the field device when in proximity of the field device, and exchange data with the field device in response to the field device verifying the temporary key.

Abstract: An air filtering apparatus including motor selectively connected to a power source, a fan driven by the motor and creating an air flow, a replaceable filter element selectively positioned in the air flow path, and an electronic control. The electronic control includes a clogged filter element detector and an indicator and a missing filter element detector. The current drawn by the fan motor is sensed by a current transformer and compared to a predetermined threshold by a comparator in each detector. If the current drawn by the fan motor is less than the clogged filter element predetermined threshold, the clogged filter element detector operates an indicator. If the current drawn by the fan motor is greater than the missing filter element predetermined threshold, the missing filter element detector operates a controller to disconnect the fan motor from the power source.