Not all phones were currently capable of receiving alerts so the minister urged people to inform their neighbours, friends, whanau and colleagues should they receive one.
The system, which involves the country's three major telcos Spark, Vodafone and 2degrees, uses cell broadcasting technology.
Messages could be targetted to cell towers within a specific area so only those potentially at risk would receive them. A Ministry of Civil Defence and Emergency Management spokesman said the system was not capable of targeting specific phones.
Phones would have to be in cellphone range and switched on in order to receive the alerts. They could over-ride the "silent" function on some phones.
As well as Civil Defence, police, the Fire Service, the Ministry of Health and the Ministry for Primary Industries has access to the system.
Faafoi emphasised that it was an additional channel to help keep people safe in an emergency and did not replace other alert systems and information channels, or the need to take action after natural warnings.
"If you feel your life may be in danger, don't wait for an official warning. Take immediate action. For example in local source tsunami, there may not be time to send an alert. Please recognise the natural warnings and get safe."
In October, unhappy New Zealanders were woken about 1.30am on a Wednesday when a test message for the system was accidentally sent by the Europe-based service provider trialling it during their daytime hours.
You can see more information, including about compatible phones, here.