Firefighters in Northern Ireland today held out the possibility of breaking their strike if a full-scale emergency occurs during the 48-hour stoppage.
Around 500 military personnel are in place ready to take on firefighting duties when the industrial action begins later.
The men and the army's fleet of 32 Green Goddesses - painted yellow for service in Northern Ireland - have been dispersed to six points around the Greater Belfast area and eight more across Northern Ireland.
But Fire Brigade Union spokesman Mr Jim Barbour admitted officers would study every alert.
He said: "We have never let the public in Northern Ireland down yet and we have no intention of letting the public down in future."
Due to the situation in Northern Ireland and the likelihood of attacks on military firefighters, another 500 troops will support them in what is being described as "escort and protection" duties.
There are real concerns among military chiefs that - as during the 1977 fire strike when troops took over - they could become targets for hotheads and that they could be called out specifically to be attacked.
The 500 chosen troops have been specially trained in firefighting techniques.
PA