Do we need visa to transit in Guangzhou for 5 hours?

We are transiting Guangzhou 5hrs on way over and 12hrs on return. I read that so long as we do not leave airport boundry and no longer than 24hrs we do not require a visa. Were is the airport boundry? Can we stay at the hotel at the airport complex is this included within the boundry, or does this mean we do not pass through customs etc within the terminal itself?