对于货船机舱的脱险通道及其内部尺寸，SOLAS CII-2/R13.4.2.1.1中有明确要求：2部彼此尽可能远离的钢梯通往该处所上部彼此类似远离的门，从门至开敞甲板设有通道。其中1部钢梯应位于一个满足第9.2.3.3条第(4)类要求的受到保护的环围内，并从其所在处所的下部通到该处所以外的安全位置。在该环围内应设有达到相同耐火完整性标准的自闭式防火门。钢梯的安装方式应使热量不能通过未隔热的固定点传入该环围内。该环围的最小内部尺寸应至少为800x800mm，并应设有应急照明。

  但海安会于2015.6.5通过的MSC.1/Circ.1511号通函，对SOLAS公约这一条做了统一解释：内部尺寸应解释为净宽，如下图所示，除船舶结构、隔热材料和设备（如有）以外，整个垂直环围可提供直径为800mm的通道。环围内的梯子可计入环围的内部尺寸。如受保护环围包括水平部分，其净宽应不小于600mm。下图为符合上述解释的可能布置的实例。

  上述解释的英原文如下：Internal dimensions should be interpreted as clear width, so that a passage having diameter of 800 mm is available throughout the vertical enclosure, as shown in figure 8, clear of ship's structure, with insulation and equipment, if any. The ladder within the enclosure can be included in the internal dimensions of the enclosure. When protected enclosures include horizontal portions their clear width should not be less than 600 mm. Figure 8 is given as example of some possible arrangements which may be in line with the above interpretation (regulation II-2/13.4.2.1.1).

  也即机舱脱险通道的墙壁到墙壁净宽至少800mm，但直梯到对面墙壁的净宽可以小于800mm（但至少600mm）。

  同时，MSC.1/Circ.1511也对机舱斜梯和梯道的具体要求，也做了统一解释：对于机舱内构成脱险通道一部分、但不位于受保护环围内的斜梯或梯道，其倾斜角度应不大于60度，宽度应不小于600mm(注意，这里不是700mm)。该要求不适用于不构成脱险通道部分，仅用于提供从位于机器处所内主平台或甲板层通向某个机器或类似区域的通道的斜梯或梯道。

  英原文：Inclined ladders/stairways in machinery spaces being part of, or providing access to, escape routes, but not located within a protected enclosure should not have an inclination greater than 60° and should not be less than 600 mm in clear width. Such requirement need not be applied to ladders/stairways not forming part of an escape route, only provided for access to equipment or components, or similar areas, from one of the main platforms or deck levels within such spaces (regulation II-2/13.4.2.1).

  提供从A类机器处所至开敞甲板的脱险通道的受保护环围，可安装一个舱口作为环围至开敞甲板的出口。该舱口的最小内部尺寸应为800x800mm。

  英原文：A protected enclosure providing escape from machinery spaces of category A to an open deck may be fitted with a hatch as means of egress from the enclosure to the open deck. The hatch should have minimum internal dimensions of 800 mm x 800 mm (regulation II-2/13.4.2.1.1).