They had to choose somehing, and 911 is:
Dial 911.
You would dial 911 for an emergency.
Canada uses 911 as its emergency number.
911
One should only dial 911 if one has an emergency.
depends what country you are in. For example, in the UK, you would dial 999 and in the USA you would dial 911.
For any emergency situation, dial 911.
Just dial number 911 on your telephone to reach an emergency operator. The emergency operator will connect you to the police, the fire department, or whatever you need. However, 911 doesn't work everywhere, the numbers can vary depending on where you live. The best way to get in touch with someone in an emergency is just dial "0" for an operator. It is best not to fake a 911 call, because it is an emergency line and if one pulls a prank call, one can receive an expensive ticket.
Dialing 911 automatically routes you to an emergency service center near your current location.
You dial 911 or the police non-emergency number if there are no serious injuries.
In the United States, dial 911, the emergency response number nationwide. If you know the emergency number for the gas company, you could dial that number as well - but from your cell phone, as you are evacuating the area.
That is going to be different for every firestation everywhere. In the US, it is usual to dial 911 in the event of an emergency, and give the information to the operator who can dispatch the appropriate emergency workers to you.