Of course this is there answer. Yet still they won't actually identify what is in Flourish Excel. For the record, the MSDS safety precautions for each are identical and continuing to pretend that it is somehow safer because it comes in a pretty(expensive) bottle is silly.
At one point Excel was simply labeled as Glutaraldehyde on the MSDS. Now they have essentially made up a name for it(that at one point they claimed to be patenting, but apparently have no grounds to patent it on).
The use of Metricide 14 in a responsible manor is safe. NO more or less dangerous than Excel. If you don't believe me, just look at the MSDS provided by seachem.
SECTION VIII: CONTROL MEASURES
Respiratory Protection NA
Ventilation Local Exhaust, Mechanical Ventilation
Protective Gloves Recommended
Eye Protection Required
Other Protective Clothing or Equipment NA
Work/Hygienic Practices Good house keeping practices