From Dota 2 Wiki
Players can use the Scan ability on the right of the minimap UI to detect any enemy heroes in an area.
- Has a global team-wide cooldown of 3.5 minutes.
- Starts on cooldown (not available at the beginning of the match).
- The button is located at the bottom right corner of the minimap border, above the Glyph of Fortification button.
- Checks for enemy presence in 1 second intervals, starting immediately on use, resulting in 9 checks.
- When a hero is detected, the green (blue in color blind mode) minimap indicator turns red.
- Does not show how many heroes there are, just if there are any enemy heroes.
- Does not give vision or reveal anything other than the presence of enemy heroes.
- Enemies do not know when your team casts it.