Carrying too heavy a stress load is like running a car engine past the red line or leaving a toaster stuck in the 'on' position.

BBC: Dealing with anger

Still, President Barack Obama declared the use, deployment or transfer of the weapons to be his "red line" for possible military intervention in the Arab country.

NPR: Commander: Contingency Plans Under Way For Syria

Both have focused on the threat posed by Bashar al-Assad's stockpiles of chemical weapons, warning that their use inside Syria, or their transfer to Hezbollah in Lebanon, would cross a "red line" that could trigger a military response.

WSJ: Obama to Visit Israel, West Bank

The folds were red and swollen so I couldn't really tell if it looked different or not, but the line between my eyebrows was gone.

FORBES: Going Under The Needle

"We have been very clear to the Assad regime -- but also to other players on the ground -- that a red line for us is, we start seeing a whole bunch of chemical weapons moving around or being utilized, " he told reporters.

CNN: Questions arise over chemical weapons claims in Syria