Which system's internal auditor wants to enter the quality department of property management enterprises to take the ISO exam? Iso 9000,9001,14000, 1400 1, OHSAS 1800 1 which is appropriate?

First of all, it is clear that many property companies do ISO system for assessment, because owners have no requirements for the property company system, and general property companies choose to establish ISO system for assessment. That is to say, evaluating excellent residential quarters or something. Therefore, general property companies only do ISO900 1, because this is enough. But at the same time, many property companies will consider the impact of enterprises on the environment, and at the same time increase the evaluation code to establish ISO 1400 1 environmental quality management system. Therefore, in order to develop, it is suggested that ISO900 1 and ISO 1400 1 study together. Although 1400 1 is based on 900 1, some people will say that 1400 1 is good, but if the foundation is 9000, I wish you a good development in the property management company!