How do I become a Technical Member?

To be recommended for Technical Member status, you should hold one of the accredited level 3 qualifications and have a suitable amount of experience in health and safety. Your experience can be gained while you're studying by voluntary activity, part time work or a full time job role, specifically in health and safety or with an operational health and safety element, for example facilities management.

Every Technical Member has to maintain their Continuing Professional Development (CPD).

What's the difference between an Associate member and a Technical member of IOSH?

Associate and Technician membership recognise the same qualifications however, by definition, a Technician member is someone who is currently practising in health and safety and possibly looking to develop their career. As a result, they need to maintain their skills and knowledge with CPD.

While Associate membership recognises health and safety knowledge, it does not reflect any experience. It is not appropriate if you’re currently practising and giving advice on health and safety unless you are new to the profession and are currently building experience.

I've taken this from the membership advice page.