That is the core advice from the U.S. Fire Administration and the EPA. The rest of this guide covers timing, where to put the can on a small lot, and how Philadelphia's trash rules fit in.
Use the right container
Use a metal bucket or can with a tight metal lid, used only for ashes. The Montgomery County, Maryland fire service tip sheet warns against plastic buckets, paper or plastic bags, and cardboard boxes, and says not to put any other combustibles in the ash can. A lid matters: an old CPSC briefing on wood-burning appliance instructions says ashes should stay in the closed container until all cinders have thoroughly cooled.
Set the can on bare ground, concrete or another noncombustible surface, not on a wood deck or near dry leaves.
Give the ashes time, and assume they are hot
The EPA's Tips for a Better Burn says to remove ashes after they have cooled, not while they are hot, because cooler ashes are much less likely to ignite. The Maryland fire service goes further: treat all ashes and coals as hot, even when you think they have had time to cool, and when possible let them sit in the fireplace or stove for several days before removing them.
There is no safe fixed deadline. How long ashes stay hot depends on how big the fire was, what burned, and how much unburned wood is left. When you do move them, wet them down in the metal can, as the USFA advises.
Two more rules from the same tip sheet: don't empty ashes outside on a windy day, since wind can wake embers and carry them, and never use a vacuum cleaner to pick up ashes.
Where to put the can on a rowhome lot
The 10-foot rule from the USFA fireplace safety card is easy on a big yard and hard on a Philadelphia rowhome block, where the back patio sits against your wall, your neighbor's wall and a wooden fence. The Maryland fire service lists garages, decks, porches, fences and wood piles as places the can should be kept away from.
If there is no spot 10 feet from every building and fence, keep the ashes in the fireplace or stove a few days longer instead of parking a warm can on the back step, the front stoop or a shared alley. Move them only when they are cold, then keep the lidded can on concrete or bare ground in the most open spot you have.
How Philadelphia's trash rules fit in
Philadelphia's refuse code, Section 9-604, lists ashes among the non-combustible wastes it defines as refuse, alongside cans, broken glass and floor sweepings. So the question is not whether they can go out, but how.
The city's residential trash rules allow metal or other non-corrodible cans no larger than 32 gallons, or sealed plastic bags of 30 to 32 gallons, and every container needs a tight-fitting lid or a secure closure. For fireplace ashes, use the metal can, not a bag. From October 1 to March 31, trash may go out between 5 p.m. the night before collection and 7 a.m. on collection day (Center City has different hours), and a single-family home is limited to four cans or eight bags a week.
Put ashes out only once they are cold to the touch all the way through, and keep them out of your regular plastic trash container.
Related fireplace precautions
The CPSC and CDC say to open the damper before lighting a fire and keep it open until the ashes are cool, because an open damper may help prevent a buildup of poisonous gases. If a smoke or CO alarm sounds, leave the house and call 911. Our guide on what a CO alarm means explains when to leave.
The USFA also says to have the chimney inspected and cleaned each year by a professional. Our creosote and chimney sweep guide covers how often, and if you are done with wood fires for good, see what to check before closing up a fireplace.
When to stop and call for help
If the ash can feels hot, smokes, or smells of burning, keep the lid on, keep it outdoors, and don't take it inside. Call 911 for any fire, smoke inside the house, or an alarm. If you suspect carbon monoxide poisoning, get fresh air and seek medical help right away, as the CPSC and CDC advise.