I had my roof replaced around September of 2020 a couple of days ago I installed a carbon monoxide alarm near the water heater and the alarm went off a couple of days later come to find out when the roofers put the vent cap on they pushed it all the way down to where the carbon monoxide was being pushed back into my house and being circulated through the house we are currently trying to figure out what health issues it has caused. All of us in the house have noticed a decline in health over the past year and a half
A contractor has an implied obligation to perform its work in a good and workmanlike manner. Not installing a vent cap properly could violate that obligation.
So, theoretically, you could sue the contractor for a breach of contract, assuming that you have sustained some monetary damages (such as correcting the installation of the vent cap).
Suing for personal injury is more difficult particularly if you cannot monetize the amount of damage.
Good luck.