Air quality was poor in the capital region on Wednesday, and meteorologists predicted that it could deteriorate elsewhere on the coast before disappearing by Thursday.
Pia Anttila, an FMI researcher, says that the ash first appeared on Wednesday morning in south-western Finland, before spreading to the Helsinki area.
According to the FMI, on Wednesday morning the worst of the ash cloud was situated along a line running from Turku to Helsinki and Kotka in the south-east. Later in the day somewhat weaker concentrations were expected to spread north toward Pori, Lappeenranta and Tampere.
The ash could adversely affect allergy sufferers, who are advised to avoid spending too much time outdoors.
The civil aviation administration Finavia said air traffic was running normally on Wednesday.
The ash cloud, which caused flight cancellations in Britain, Germany and the Nordic region, was expected to dissipate overnight, the air traffic agency Eurocontrol said on Wednesday evening.
"Tomorrow, we do not expect any significant impact on European airspace," Eurocontrol said. About 450 flights were affected in Germany on Wednesday mainly at Berlin, Bremen and Hamburg airports, the agency said.
