Containment is about the edge, not the flames
A fire that is 45% contained is not 45% extinguished. Containment means crews have built control line, a fuel break the fire is not expected to cross, around 45% of the fire's perimeter. Control lines can be bulldozed or hand-dug ground stripped to bare soil, a river or road, or an area already burned out on purpose.
The National Wildfire Coordinating Group defines a contained fire as one whose spread has been halted by control lines, and a controlled fire as one where those lines are secure enough that no further spread is expected. "Out" comes later still, after crews verify no heat remains near the lines.
Why containment can stall or even drop
Containment percentages routinely sit at 0% for days on large fires. That usually means the fire is burning in terrain too dangerous or remote for direct attack, not that nobody is fighting it. Crews may be working miles ahead of the fire, preparing lines where they can actually hold it.
Containment can also go backwards. If wind pushes fire across a control line, the compromised section no longer counts, and the reported percentage drops. A fire at high containment during a major wind event still deserves attention.
How to read containment together with other numbers
Acres tell you how big a fire is; containment tells you how secure its edge is; growth since the last report tells you its momentum. A 100,000-acre fire at 90% containment with no recent growth is usually far less dangerous than a 5,000-acre fire at 0% burning toward homes in high wind.
On Fire Nearby, flame icons are tinted by containment so you can scan a region at a glance: red flames are uncontained, green flames are effectively secured.
Frequently asked questions
Not necessarily. Full containment means control lines surround the fire and are expected to hold. Interior islands of fuel can keep burning and smoking for weeks until the fire is declared controlled and then out.
The incident management team assigned to the fire reports containment through official incident status summaries (ICS-209), which flow into national reporting systems like the ones this site reads.
Official sources
This guide summarizes the following government publications. Read them for full detail.
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