AS 3961:2017 The storage and handling of liquefied natural gas.
2.6.8 Ignition sources
An ignition source shall not fall within a Zone 0, I, or 2 hazardous area, as defined in AS/NZS 60079.10.1 and illustrated in Appendix C of this Standard.
Where an opening into a building intersects a hazardous area, the whole of the interior of the building shall be taken to have assumed the same zone.
Where a pit, trench or duct has an opening into a hazardous area, the zone shall be determined as follows:
(a) If the potential gas escape will be vapour only. an open trench or pit is unzoned. and an enclosed drain assumes the same zone as that which it intersects.
(b) If the potential escape is liquefied natural gas, the duct, drain, pit, or the like becomes Zone I over its length, irrespective of whether it is open or closed.
(c) The whole of the interior of any duct containing a pipe joint becomes the same zone as that for the vicinity of the joint.
2.6.9 Use of vapour harriers and firesalls
Separation distances may be measured in a horizontal plane around the end of any intervening vapour barrier or firewall complying with Clause 2.6.11 or Clause 2.6.12 provided that
(a) the top of the vapour barrier shall extend above the hazardous area:
(b) the clearance between the vapour barrier and the tank shall comply with Clause 2.6.13(b): and
(c) where the separation distance under consideration involves a protected place, the vapour barrier shall also be a firewall (see Clause 2.6.11).
2.6.10 (‘onstruction of vapour harriers
A vapour barrier shall comply with the following requirements:
(a) The vapour barrier shall be impervious to gas over the whole of the area of the barrier around which a separation distance is to be measured.
(b) The vapour barrier shall be made of material that is non-combustible and the construction shall be sufficiently durable to remain functional as a vapour barrier for the life of the installation.
2.6.11 Construction of firewalls
A firewall shall comply with the requirements for vapour barriers, and in addition shall have an FRL at least FRL 240/240/240.
2.6.12 Use of existing construction
Existing building walls or fences may be used as vapour barriers or firewalls provided that they comply with the appropriate requirements.
2.6.13 Ventilation and access
The installation site for storage shall comply with the following requirements for ventilation and access:
(a) Storage tanks shall be in the open air outside buildings.
(b) Nearby construction, fences, walls, vapour barriers or the like shall permit free access around and cross-ventilation for the tank.
Any construction that is not higher than the bottom of the tank shall not be treated as being a ventilation obstruction.AS 3961 pdf download.