How to get rid of CO₂ in a house with A/C in hot summer?

That's a really high CO₂ level. You need to figure out what is causing it and fix that, it's not normal.

Gas fired appliances with leaky vents are the most likely suspects — hot water heater, dryer? (Probably not your furnace, since its summer!)

In the meantime I would seriously open some windows and suck it up, that's dangerously high if accurate.

You can also try this: Get some plants in places where there's high co2 concentration. If there's no sun, then use plants which are good in that situation.

What type of air condition are you using? Some only cool the air inside, while others use fresh air from outside. In a cafe or club there are norms about how much fresh air the air condition must put inside during a given period of time.

I would suggest the following:

1. measure the CO₂ concentration outside to compare it with your inside CO₂ concentrations.
2. Measure CO₂ concentration on a Sunday while you stay at home. Does it increase the same amount?
3. Try to calculate how much O₂ you turn to CO₂ while you sleep and make an estimate of how large the CO₂ concentration should be after one night. If it is much higher than it could be just by your breathing, search for other things that may increase CO₂ in your room.

Plants respire throughout the day, producing both O² and CO². They produce much more oxygen than CO² though. It is a good idea to have plants to help with air, but they don't produce enough to make a huge difference. People intake approximately 750L of oxygen per day. We exhale approximately 0.02 cubic meters of CO² per hour. A plant, on average, produces approximately 22L of oxygen per day. It would take a lot of plants to change your room's exchange. That doesn't mean it is a bad idea though. Everything helps. Specific plants exchange better than others, and some help to remove harmful pollutants from the air. Do not fall victim to the myth that plants exchange CO² only at night and that they come even close to an even exchange. They exchange far more oxygen and do help.

I have asthma and an 80% collapsed windpipe. With CO2 levels even within a good range (less than 600 ppm) I become short of breath. I had an erv system(energy recovery ventilation)system installed. Can’t use that during fire season! It hasn’t helped at all and the installers haven’t been helpful in figuring out why an open window does a better job. When I use it Particulate matter increases and opening windows does a better job of lowering CO2. The best idea I’ve found is to reverse a powerful fan out of the window to pull CO2 from the room. In minutes I can reduce the level but I can only rely on this method in the spring and fall unfortunately.