Measurement is fundamental to control which is necessary for both health and environmental reasons. Without measurement it is impossible to establish baselines, identify sources and assess improvements. Controlling losses can also save the site operator millions of dollars.

Health

Many of the species which can be measured by DIAL have an adverse effect on health. For example, VOC emissions are implicated directly and indirectly in many health issues.

The principle health concern arising directly from atmospheric VOCs is from long term exposure to low levels of those which are known or suspected to be carcinogens. For example benzene is a genotoxic (causes cancer by reacting directly with the DNA in cell material) and has a current DoE Expert Panel on Air Quality Standards (EPAQS) recommended limit of 5 ppb (reducing to 1 ppb) taken as a running annual average. Indirectly, VOCs can effect health as a result of their role in the production of tropospheric ozone (see below).

Environment

Ozone is produced in the lower atmosphere by reaction with oxygen and oxides of nitrogen in the presence of sunlight. In "unpolluted" atmospheres these reactions are in equilibrium, ozone is created and destroyed and there is no net ozone production.

However, most VOCs contribute, in varying degrees, to the net production of tropospheric ozone by effectively interfering with the equilibrium. Such VOCs produce peroxy radicals in the presence of sunlight (photochemically) and these, in turn, oxidise nitric oxide to nitrogen dioxide, resulting in a net production of ozone.

Long term exposure has been seen to damage vegetation and materials. Ozone is also a greenhouse gas and because of their role in ozone formation VOCs are contributors to global warming, and are subject to the 1992 Climate Change Convention and the Kyoto summit agreements.

Financial savings

With a knowledge of sources (of VOCs), a site can effectively target maintenance programmes. This can generate a financial benefit through reducing the loss of valuable refined species. For example, at one refinery we surveyed in Sweden the reduction in VOC emissions they were able to make after our visit gives a saving to the company of $1 million per annum, on a conservative estimate

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