Poison Emission is the ability to emit a potent toxin that kills people within an unspecified radius.
The power's range does not seem to be limited, as Maya Herrera was able to kill an entire wedding reception from inside a tent. However, on other occasions, her power seemed to be restricted to the room she was in- it is possible that she lacked the adrenaline or willpower on those occasions.
When this power is used, the evolved human's eyes turn black, and she/he cries black tears. The effects on people in the vicinity seem to be immediate, with no known method of defense. Within seconds, the victims' own eyes start to darken and secrete black tears. They appear breathless and in great pain as they die. The effects of this power could be counteracted by the user or a post-human with Alejandro's ability.
In Maya's case, the people affected by her ability who hadn't yet died recovered, as if unharmed but still fully aware of what had happened to them.
When Maya first gained her ability her emotions controlled it, if she was angry or distressed she would not be able to control it until she met Sylar, who helped her be able to control her ability.
It is noted that their corpses leaked black blood when cut open.