An investigation has been launched into how a chemical which causes irritation to eyes, nose and skin leaked out of a tank at Grangemouth port.
Emergency services were at the docks throughout the night
A major incident was declared on Wednesday when the vapour caused a large plume above the Forth.
The chemical, which was inside a storage tank on a quayside within the docks area, was Divinylbenzene.
No-one was injured in the incident, however some residents have expressed concern about a lack of information.
The chemical, understood to be delivered on a regular basis, had been unloaded from a cargo vessel and was due to be delivered to Rohm and Haas, which has a facility in Grangemouth.
The incident happened away from Scotland's largest oil refinery in Grangemouth which is run by Innovene.
Pale straw-coloured liquid
Used in making plastics and resins
Volatile between 30C and 95C
Exposure caused by breathing in vapours or contact with skin
Can cause irritation to eyes and nose
Little information on long-term health effects
Fire and rescue personnel kept the storage container cooled with water jets overnight and Central Scotland Police said on Thursday morning that people could "go about their normal business".
Nearby residents were not evacuated but were instead advised to stay inside and keep doors and windows closed.
One resident, Julie White, said she only found out about the incident by chance at about 2300 BST and that the information she did receive was very confusing.
"I just think it's concerning because I've got a boy who's six years old," she said.
Another resident, Audrey Dulson, 32, of Grangeburn Road, said she first heard of the incident early on Thursday morning.
"We slept with all of the windows open last night because we didn't know and both my daughter and the dogs were out playing yesterday evening," she said.
"It makes me annoyed that they didn't use a tannoy or a siren to let us know that there was a leak."
Resident Audrey Dulson said there should have been a warning siren
Friends of the Earth Scotland chief executive, Duncan McLaren, said residents should have been better informed.
"I'm very disturbed that the public weren't informed much more directly about this incident," he said.
"I'm also very disturbed that the emergency services were apparently unable to establish what the chemical was for over 12 hours.
"Part of the plan should be to go house to house in the area that is potentially affected."
He said the chemical was among thousands that should be phased out or at least more test data made available on its long-term effects.
The police confirmed that a major multi-agency response was established to deal with the incident.
It involved Central Scotland Police, Central Scotland Fire and Rescue Service, Falkirk Council, Sepa, the Health and Safety Executive, Forth Valley Health Board, Forth Ports, the Scottish Executive and industry partners.
This was established under the Central Scotland Strategic Co-ordinating Group protocols.