The Association of Electoral Administrators (AEA) - a body for electoral staff, which has more than 1, 700 members - also criticised the timing of the PCC elections, saying it was "not in the interests of voters".

BBC: Police and crime commissioner elections 'failed voters'

The report by AEA technology said emissions of the gases, used in refrigeration, air-conditioning and heat pump systems, were "relatively small" at 3.9% of the total but were increasing.

BBC: Guernsey greenhouse gas decrease continues

AEA's engineers have exploited this reactivity (and also enhanced its effectiveness at exhaust-pipe temperatures, in ways they are reluctant to discuss) to burn up the undesirable particles and other carbon-rich pollutants.

ECONOMIST: Diesel engines