I opened a basement window and then the front door to the house. This caused the level to drop down to 56 ppm, according to the loud and annoying meter, and then caused the stairwell CO meter to start going off with its own, different sound.
Cacophony! So peaceful.
I opened the back door to the house, and the garage door, and opened the bathroom window wider than it already was open. After a few more minutes, the squawking from both meters stopped.
I can't really open more than this as one of the two feline residents likes to go explore the big room and make it his territory whenever he gets the chance. (The screen doors are keeping him from taking advantage of the situation, so far, but this is not for lack of his trying.)
I am unfamiliar with what devices in the house are generating CO, so I have not attempted to address the causes. I have also not called the emergency services.
The homeowner is away from desk (probably at lunch) and not responding to telephone calls.
What else should I do?
(I would prefer not to abandon the cats, as the younger female cat is already traumatized from the loud noises made by the workmen installing insulation in the attic this morning. The male is entirely unruffled and continuing his single-minded pursuit of an escape route.)
ETA: The homeowner just answered my voicemail and told me to leave the house. I am sitting on the front porch with the laptop.