The Blast Box has many of the same properties of a normal crate in that it is heavy, making it hard to carry except for a few characters. However, when thrown, it will not always explode. Instead, a threshold of damage of around 30% must be reached before it explodes. Flames will cause the explosion immediately. The explosion has a great amount of vertical knockback that can KO at high enough percents. A well-timed projectile can be used to strategically set it off around opponents.
It curiously can appear from inside crates and capsules despite being a heavy item.
Super Smash Bros. Brawl
An explosive-filled box that will detonate when the box is broken. The box can be smashed with normal attacks and will also catch fire and blow up if it's exposed to any flame. Unlike ordinary crates, blast boxes do not change their appearance from stage to stage. There's one fundamental rule when dealing with these items: be out of range when they blow.
Wii - Super Smash Bros. Brawl
Super Smash Bros. for 3DS/ Wii U
A highly flammable box packed full of gunpowder. The player who last threw the box will get credit for any KOs it causes. Setting off the box will result in a massive explosion, and you've only yourself to blame if you blow yourself up. It says DANGER right on the front.