The control centre which deals with 999 calls across East Sussex is to move out of the county.
Unions say it is a cost-cutting measure which will compromise safety but the fire service says it will create a more joined-up approach.
The controversial decision was made behind closed doors at a meeting of the fire service on Thursday, reducing some of the staff involved to tears.
The chairman used his casting vote to exclude the press and the public, on the grounds that some of the financial information being discussed was confidential.
Under the plans, the control centre for East Sussex Fire & Rescue will join the West Sussex control centre, which is shared with Surrey Fire & Rescue in Salfords near Redhill.
It is currently based in Haywards Heath which is approximately 20 miles away from the new site.
The fire service aims to answer emergency calls within five seconds and mobilise crews within 2 minutes.
It says it has some of the best response times in the country and intends to maintain them.
Staff had put forward an alternative plan to establish a new stand-alone control centre for East Sussex, within the county, at the headquarters the fire service already shares with Sussex Police.
However, that was voted against as being too expensive.
The move will take place in the spring of 2021.