IEC 60721-3-4:20 19对产品安装在非防风雨位置固定使用时所受到的环境参数组及其严重程度进行了分类。IEC 60721-3-3中规定了产品可永久或临时固定使用的防风雨位置。 这第三版取消并取代了1995年出版的第二版和修正案1:19 96。本版构成技术修订版。 与上一版相比，此版本包括以下重大技术变更: a)第1条:重新措辞。 b)第2条:规范性参考文献已更新。 c)第3条:定义已更新。 d)第4条:重新措辞和简化。 e)第5条:修订和更新。基于使用从参考技术报告中获得的新信息，一些类别已被全新的类别所取代。f)化学活性物质的定义值现在参考ISO 9223。 g)表1至表5:更新。

IEC 60721-3-4:2019 classifies groups of environmental parameters and their severities to which products are subjected when installed for stationary use at non-weatherprotected locations. Weatherprotected locations where products can be mounted for stationary use permanently or temporarily are addressed in IEC 60721-3-3.
This third edition cancels and replaces the second edition published in 1995 and Amendment 1:1996. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) Clause 1: reworded.
b) Clause 2: normative references have been updated.
c) Clause 3: definitions have been updated.
d) Clause 4: reworded and simplified.
e) Clause 5: revised and updated. Several classes have been replaced by completely new classes based on the use of new information obtained from referenced technical reports.
f) Defined values of chemically active substances are now by reference to ISO 9223.
g) Tables 1 through 5: updated.