A chemical firm has been fined £10,000 after an orange cloud of gas escaped from its premises on South Tyneside.
Industrial Chemicals Ltd pleaded guilty to two permit breaches at its Hebburn site in September 2010.
As a result of failing to follow site procedures, excess amounts of nitrogen dioxide were produced, South Tyneside magistrates heard.
The Essex-based company has since put measures in place to prevent a similar incident happening.
As well as the fine, it had to pay costs of £5,600 to the Environment Agency, which brought the case.
The gas escape happened during the production of ferric sulphate, used in sewerage treatment.
Too much acid was added, leading to excess amounts of nitrogen dioxide which escaped from the reactor into the air for about 30 minutes before the plant was shut down.
Magistrates were told that an orange gas cloud was blown east towards Jarrow but dispersed before any harm could be caused.
Speaking after the case, Peter Duffy, from the Environment Agency, said: "This was a potentially serious incident, and had the prevailing wind been in a different direction, it could have been much worse.
"The company failed to follow its site procedures which resulted in the incident.
"Operating procedures are there to ensure that plants like this don't cause any harm to the public or the environment.
"Since the incident we have been working with the company to improve procedures at the site."