Here is a quick walkthrough for buying and downloading the official PDF:
Procedures for verifying that an installation remains safe over time. Important Note on Versions
No. ABNT does not provide official free PDFs of NBR 5410. Only free reading at physical consultation points is available. Beware of any website claiming to offer a "free ABNT download."
Many companies and universities provide access to standards through the Target GEDWeb system, which allows authorized users to view and download the full text.
Guidelines to prevent fires and equipment damage from overheating.