I need help calculating the CR of a trap that sprays nightmare vapor. The core rulebook lists how serveral types of poisons affect trap CR, but not this one, which is a problem for me. Trap CR in general is also rather confusing.
Here's the trap:
A large trapdoor is built into the floor. It has two handles on opposite edges that hold it shut. Squeezing both handles together unlocks the trapdoor (though only for as long as they are both squeezed, as they are spring-loaded to lock when let go of). Jamming a handle into the open position requires a DC 15 Disable Device check, and each handle needs to be disabled individually (though really, once one is open there's no reason to disable the second).
A medium-sized PC can reach both handles at once by moving close to the trapdoor and reaching as far as possible with both arms in opposite directions, gripping both handles at once and lifting the door. Doing so however requires the PC to position themselves directly in front of the door while opening it. (A small PC cannot reach both handles at once. Two PCs working together can grip opposite handles without needing to stand directly in front of the door.)
When the trapdoor is opened, a small burst of nightmare vapor sprays into the square directly in front of the trapdoor (No save to dodge the spray, Fort save to resist the poison). It dissipates immediately after spraying, and not enough poison is sprayed to affect any other squares as it dissipates.
Bumping this, as I still don't know how it would be calculated, and would still like some help.
Bump. Again. I find it hard to believe that nobody knows how to do this.