Fire crews and gardai were called to the industrial estate in Baldoyle, Co Dublin, after a security guard reported a chemical odour at 3.30a.m. yesterday.
Production operations at Newport Synthesis Ltd were suspended until the matter was investigated.
The emergency services left after half an hour, being satisfied there was no problem on site.
The company said its investigations were continuing but "no obvious source of emissions can be identified. All potential sources of emission are being investigated and will be carefully monitored when production operations recommence today".