PROVIDENCE — Fire Chief George S. Farrell has issued a general order limiting the use of fire and rescue apparatus, in part due to the labor unrest that has resurfaced during the annual meeting of the U.S. Conference of Mayors.

For example, the order states in effect: Take the most direct route possible to return to your fire house after an incident, rather than driving by a firefighter demonstration to show solidarity with your union brethren. And do not blow the air horn on your vehicle when returning.

The order, issued Thursday, spells out when apparatus may be driven out of fire houses and where they may go. It declares off-limits the vicinities of seven conference venues, such as Manton Avenue and Aleppo Street, where mayors plan to help Mayor David N. Cicilline work on a playground Sunday — unless there is an emergency.

Paul A. Doughty, president of the firefighters union, dismissed the order as a direct swipe at the picketing and “clearly retaliation” that limits the discretion usually exercised by firefighters below the rank of chief officer.

“In 23 years, I’ve never seen anything like this come out,” Doughty commented. For example, he said, there was no rule saying that vehicle drivers had to take the most direct route back to a fire house.

Farrell acknowledged the link between the order and the unrest, but he said it also arises from operational concerns not generally known by the firefighters during a conference that has attracted dignitaries from the United States and abroad.

And he said that he is concerned about the image of firefighters and the Fire Department. Given the economic recession and some people’s anger toward firefighters’ compensation and the use of government vehicles, it makes sense to be discreet, he said.

The mayor of North Providence recently clashed with the firefighters union in his town over the use of city vehicles to get lunch, to shop or for any other nonofficial purpose.

Farrell ordered firefighters not to congregate outside fire houses and company officers to keep the vehicles inside the fire houses with the overhead doors shut unless a vehicle has to come or go. The image of firefighters lounging idle near a fire house does not go down with the public very well these days, Farrell said.

Much of the general order is a reiteration of preexisting policy, he contended, and by renewing a notice of it, he said that he hopes to save a firefighter or two from being disciplined for an infraction.

gsmith@projo.com