.1 Enclosed spaces containing any part of the
mud circulating system that has an opening into the spaces and is
between the well and the final degassing discharge.
.2 Enclosed spaces or semi-enclosed locations
that are below the drill floor and contain a possible source of release
such as the top of a drilling nipple.
.3 Outdoor locations below the drill floor and
within a radius of 1.5 m from a possible source of release such as
the top of a drilling nipple.
.4 Enclosed spaces that are on the drill floor
and which are not separated by a solid floor from the spaces in paragraph
6.2.3.2.
.5 In outdoor or semi-enclosed locations, except
as provided for in paragraph 6.2.3.2, the area within 1.5 m from the
boundaries of any openings to equipment which is part of the mud system
as specified in paragraph 6.2.3.1, any ventilation outlets of zone
1 spaces, or any access to zone 1 spaces.
.6 Pits, ducts or similar structures in locations
which would otherwise be zone 2 but which are so arranged that dispersion
of gas may not occur.