Felar Inherent:
"Detect Scent"
Command invoked "Detectscent"
Skill "Detect Scent: Modifies None by 0 for 10 hours"
Skill "Detect Scent: Modifies Constitution by -2 for 10 hours"

"detectscent"
Your olfactory awareness heightens as you search for scents on the breeze.

When detecting a scent outdoors:
"An unfamiliar odor wafts toward you on the breeze."

When detecting a scent indoors:
"Your hackles raise as you detect the lingering presence of an unfamiliar scent."

Detect Scent Helpfile

Using their inherent olfactory abilities, felar are able to search for unfamiliar scents on the wind, possibly alerting them to others within the same area. Because of the delicate nature of detecting the faintest odors, weather conditions must be ideal or the scent will be masked from detection. Also, due to the pungent mix of odors in most indoor areas, felar will only be able to detect the scent of others who have already been in the area for some time. The strain of searching for minute smells tends to be someone draining, and can only be endured once per day.

To sum it up:

During non rainy/windy conditions, felar have a danger sense alerting them to others in the area. When indoors, there is a two tick delay upon when someone enters the area, and when the felar is alerted. The ability can only be invoked once per day, and lasts 10 hours.