Working fire crews attended 11 incidents across Essex during the strike by FBU members this morning.
The industrial action started at 6am and ended at 8am, but FBU members will strike again later at 11pm.
Incidents have included six false alarms and two incidents involving flood water where electrics were involved.
A fire service spokesman said: "Members of the public should continue to dial 999 in an emergency and working Essex crews will attend.
"Businesses should follow up automatic alarms with a phone call to ensure attendance during periods of reduced fire cover."
Further strike will take place over the weekend as follows:
Friday July 18: 6am–8am and 11pm–1am on Saturday 19 July
Saturday July 19: 11am–1pm and 11pm–1am on Sunday 20 July
Sunday July 20: 5pm–7pm
Monday July 21: 6am–8am and 5pm–7pm