The planned four-hour walkout from midday is part of an on-going dispute with the Government over pensions.
People are being urged to reduce the risk of fire in their properties, for example, by taking extra care when cooking, making sure smoke detectors are fitted and disposing of cigarettes safely.
A skeleton service is due to operate during the stoppage, with cover provided in the main by firefighters who are not part of the union, working alongside a small number of auxiliary firefighters who have received training to provide basic support.
AF&RS says it will prioritise calls to emergencies where there is a risk to life. Chief Fire Officer Kevin Pearson said: “This is a national dispute over which Avon Fire Authority has no control.
“Although we have contingency arrangements in place, the reality is we will not be in a position to provide the excellent emergency response we usually do.”