21.   The defects, authorities said, sometimes would cause false readings.

22.   The laboratory tests were conducted after initial field tests on batches of mail sent to both institutions recorded what turned out to be false positive readings.

23.   The machines have returned false readings before.

24.   The sources said that if the sabotage had not been discovered before takeoff, the false readings could have misled the pilot and caused a disaster.

25.   They had been working from home since Monday, when a preliminary field test registered what turned out to be a false positive reading for anthrax.

26.   Women especially may get false readings.

27.   The AAIB said one Airbus operator carried an extra two tonnes of fuel as a precaution against false readings.

28.   That would give you a false reading for what is to come.