Fire Shield
A Fire Shield behaves the same as the standard Shield, except for two things.
The fire shield will periodically create a burst of fire, which burns aliens. This works in a similar way to Evolve, where you will see a progress bar under your ship which ticks down to zero. If you also have Evolve enabled on your ship, the Evolve cool-off is on the left-hand side and the shield cool-off is on the right-hand side:
Once it reaches zero, the shield will emit a burst of fire, like so, which causes damage to aliens:
When you activate the shield, the shield itself will be covered in fire. This allows you to attack aliens whilst the shield is active.
As with the normal shield, the Fire Shield will show a count-down of how long the shield is active for.