An ammonia leak caused by a faulty valve has led to several Mount streets being shut down.

Employees of Realcool Cold Storage Ltd were evacuated from their premises at the Mount early this afternoon after the leak was detected.

Realcool employee Koby Bergersen was in the smoko room when the ammonia alarm went off.

'It's quite serious went that alarm sounds. We all got our stuff and began to evacuate.”

He says the effect of the ammonia was potent.

'It almost dropped me. It makes you go all dizzy and nauseous.”

His colleague Anthony Wairepo says someone turned on a valve by mistake, which then failed to turn back off again.

Realcool employee Anthony Wairepo.

He says the emergency services will likely wait until the silo storing the ammonia is entirely emptied and the gas dissolved before a specialist hazmat team from Rotorua enters the building.

He worries about how the incident will affect the business, which needs a good supply of ammonia to run its refrigeration units.

'Our jobs are on the line, too.”

Emergency services have shut down the entire block from Triton Avenue up to Hull Road, between Totara Street and Tukorako Drive.