Five-Alarm Fire — ruling 1

Five-Alarm Fire’s first ability triggers once for each time a creature you control deals combat damage, even if it deals combat damage to more than one creature, planeswalker, or player. For example, an attacking creature with trample that deals combat damage to a blocking creature and the defending player will cause Five-Alarm Fire’s ability to trigger once. A creature with double strike, however, may cause Five-Alarm Fire’s ability to trigger twice during a single combat.

Five-Alarm Fire : règles, fonctionnement et interactions (MTG)

Five-Alarm Fire is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Whenever a creature you control deals combat damage, put a blaze counter on this enchantment. Remove five blaze counters from this enchantment: It deals 5 damage to any target.

How it works : Five-Alarm Fire

Original English text — Wizards of the Coast / Scryfall

#1January 24, 2013· Wizards of the Coast
Five-Alarm Fire’s first ability triggers once for each time a creature you control deals combat damage, even if it deals combat damage to more than one creature, planeswalker, or player. For example, an attacking creature with trample that deals combat damage to a blocking creature and the defending player will cause Five-Alarm Fire’s ability to trigger once. A creature with double strike, however, may cause Five-Alarm Fire’s ability to trigger twice during a single combat.
No other card is named in this ruling.