While the official BIS Standards Portal typically requires a paid subscription or individual purchase for high-quality, authorized copies, you can access the document for free via the Public Resource or the Internet Archive , where it is shared under "Right to Information" public safety transparency initiatives.
No official free app. BIS has a mobile site, but you still need to purchase the PDF. Some scammers offer “free BIS standards app”—avoid them; they are data harvesters. is 3646 part 5 pdf free