ABSTRACT
Monitoring does not usually involve measuring, but it may do in special cases – this can be illustrated by examples. • The majority of monitoring of car tyre pressure involves visual inspection, without measuring. However,
when visual inspection suggests that a tyre is deflating, then the pressure is measured to check this. • There are various gases, such as carbon monoxide and carbon dioxide, which humans cannot detect. The
only way of monitoring the presence of these gases is, therefore, to have instruments which measure their concentration in the atmosphere.
