The phrase "danger zone" refers to an area or situation where there is a high level of risk or potential harm. It implies that caution needs to be taken as it could be dangerous. Full definition
Or may be there are more people living in danger zones now then ever. (hubpages.com)
In this routine, we may be stuck in a chronic low - grade inflammation danger zone for most of our lives. (nutritionfacts.org)
Just six months ago, the world entered a new danger zone when concentrations of carbon dioxide in the atmosphere passed 400 parts per million for the first time in recorded history. (theguardian.com)