One of the most misleading distortions being floated by political opponents of the Iran nuclear deal is the "24-day" loophole meme: Iran would be able to hide all evidence of any nefarious nuclear weapons work during the 24 days it may take inspectors to gain access to a suspicious site.
For starters, International Atomic Energy Agency inspectors would have continuous daily access to all of Iran's declared nuclear facilities. If Iran does not allow anytime inspections of any declared site, it could result in the reimposition — or "snapback" — of sanctions.
The 24-day rule applies only to undeclared suspect sites anywhere in the country. Because inspections anywhere at any time can be complicated to work out, a procedure was devised to address the problem.