Question No. 1
How many tyres will the unit monitor?
The TPMS will monitor the air pressure and temperature of up to 22 tyres with a pressure range of 0 to 145 psi as long as the furthest sensor is no more than 7.6 meters from the monitor. You can increase the range by a further 8 meters using a booster (Part No. 1020) as a mid point link to the monitor and the furthest sensor.

Question No. 2
Is there any chance of the sensor leaking air at the valve?
The sensors are screwed onto the valves - the exact same way the valve caps are currently screwed onto the head of each tyre valve. The valve would have to fail in the first instance and this would alert the sensor to a tyre pressure variance and would therefore sound the alarm as well as signal the flashing red led light on the tyre monitor located in the vehicle.