Enclosing the furnace and water heater?

I'd like to build some walls and access panels around these and connect to the window to exhaust what ever gases. Good idea? Maybe better to install a vent?

Are the high-efficiency units?
If not, you may create negative pressure in the utility closet without make-up air.

With heat and return ducts you can't seal this room anyway, the only time sealing is needed is when the unit is in the garage and you want to stop auto exhaust gases from entering the system.

It's a new high efficacy with the 2 pipes going out. The duct vents would not be in the utility room, the walls would be build around it.

I've got the windows closed in the basement to keep the humidity out, air doesn't seem to good down there. I guess i should install a vent to suck out the bad air? I would like to put a wall there to separate it and it could use the one window tp draft out co2.

co2 shouldn't be a problem with the new furnace, but you could install a co2 detectore to be on the safe side. If you are not conditioning the basement in the summer then you should be venting it just like a crawl space, you will have more humidity inside than out.

yes i detectored last fall and the thing went off like crazy so i called the local gas man, seems very professional he checked over everything, he said a bit was normal to have some gas and co2 down there.
I think it's coming from the gas water heater with stainless steel vent. I wonder can i enclose the gas water heater would i need another vent?

Yes it will need fire air.

Actually, you are talking about a CO detector since CO is Carbon Monoxide. CO2 is Carbon Dioxide.

I built a closet around my electric water heater and freezer with louvered door and installed a ceiling exhaust van to exhaust the heat in summer. I cut it off in winter to use the heat for the room. Dryer exhaust hose also goes out through the closet to the attic. We also hang wet clothes in there to dry on hangers so they don't require ironing.

The two pipes on your furnace are for combustion air and flue gases. Hopefully, the system is tight and it has a net neutral effect on the air in the basement. The gas water heater also needs air for combustion and the flue gases draft additional air as they flow into the flue. Usually, a basement has enough air volume to support the water heater combustion. However, other appliances, such as a dryer, can also be competing for air in the basement. Additionally, other exhaust fans within the home can also be pulling air from the basement.

I think the first place to start is with the water heater. Run the hot water heater until the burner comes on. Then, check the flue to make sure that air is flowing into it. You can do that with an incense stick or carefully with you hands (if you feel hot air coming out of the flue entrance, it is backdrafting). If the flue is backdrafting, it likely is the issue. If hot air is not coming out of the flue, run the furnace too and recheck. Then, try the dryer. Continue with various exhaust fans in the home until you find what may be causing the issue. In the end, you may need to install a makeup air duct to provide combustion air for the water heater.

If you are having issues with moisture in the basement, you should be checking your roof drainage and the grade around the foundation to make sure that excess water is not being put around the foundation. I also recommend that all basement have a dehumidifier set up to operate constantly on the humidifier control. I recommend setting the control for 60% and set the unit up to drain constantly into a floor drain rather than using the reservoir.