The operator switches the instrument on, then attaches a new mouthpiece to the sampling port. He or she then instructs the subject to blow through it until the sample is taken. A short time later their alcohol level is shown on the clear, easy-to-read display: this is illuminated, for use at night.
This is for fast yet accurate fully quantitative breath analysis, and can be used literally anywhere. It uses the Lion fuel cell sensor, so the reading is very unlikely to be affected by anything in the subject’s breath other than alcohol. The 400 is fully automatic, through microprocessor control, so it is very simple to use.
It is used extensively by Police Forces around the world, for both screening and evidential testing, and [in its SL-400 format] is Type Approved by the Home Office, Great Britain, for UK Police use in the United Kingdom.
When the reading has been taken, the operator removes and discards the mouthpiece. After a short delay the instrument is ready to use again on the next subject, as required. The result of the last test can be recalled to the display, if required.