is to use/is to be used

[navi tasan]

Which are correct:
1-This door is to be used in case of emergency.
2-This door is to use in case of emergency.
3-This door is for using in case of emergency.

In which case:
a-The door must be used in case of emergency
in which case:
b-The door can be used in case of emergency

Gratefully,
Navi.

[Raymott]

"Emergency Door"

1. is correct.
a - There are no doors that must be used in all emergencies. b. is not right either. 'Should' is better than 'must' and 'can' here.

How about c? - This door is the door which should be used in an emergency, if the emergency is such that you need to evacuate the building/room.

[Tdol]

I'd use 1 and think that 3 is not correct.

[Barb_D]

Use this door for an emergency evaculation. -- Verbal instructions while giving a tour.
"Emergency Exit" -- sign on the door.

If you are not supposed to use that door otherwise: Use this door only for an emergency evacuation. "Emergency Exit Only"
If you are not suppposed to use any other door (which seem like a bad safety plan - what if it's blocked?): Use ONLY this door for an emergency evacuation.

[bhaisahab]

Use this door for an emergency evaculation. -- Verbal instructions while giving a tour.
"Emergency Exit" -- sign on the door.

If you are not supposed to use that door otherwise: Use this door only for an emergency evacuation. "Emergency Exit Only"
If you are not suppposed to use any other door (which seem like a bad safety plan - what if it's blocked?): Use ONLY this door for an emergency evacuation.

In the UK a blocked emergency exit in any building to which the public, or above a certain number of employees, have regular access is an offence under health and safety regulations.

[Barb_D]

I like my new word - evaculation.
I was thinking more like "the fire is in the hallway where this door is" not "there are stacks of boxes in front of it."