Flower room has water heater...ramifications?

I have a 7x6 walk-in closet I am converting to a flowering room. The house's water heater is located in the back corner. It is a natural gas heater. Should I close it off from the room?
I expect that it will increase ambient room temp.
I will be using a 1000W and 600W HPS.
The closet is basically in the center of the house so intake will be off an AC cooled bedroom. Exhaust will be through the roof.
Will the water heater provide CO2? If so, would it be best to keep as exposed as possible? I have read that the average water heat emits 2 tons of CO2 per year. However, it is vented up through the ceiling so I don't know how much, if any, CO2 is released into the closet. I also know CO is deadly.
There is an intake vent currently near the base of the water heater which leads to a crawl space and provides oxygen for the combustion. There is an open access to the crawl space from our back yard, 30 feet from the vent. I'm concerned this could lead to pests. If I seal of this vent, would the plants provide enough oxygen for the water heater?
Is there more to it which I'm overlooking?

i'd keep my stuff seperate.

water heater = necessity
weed crop = luxury

i def. would not have the waterheaters only source of oxygen the plants. and like you said co2 is really dangerous, so be careful!

is there any way for you 2 frame off the water heater from the rest of the room? the heater is going to produce a lot of heat and humidity,i had that problem and i built a insulated wall to protect the room.

also i wouldnt think that a water heater wouldnt be putting out co2 unless an over flow valve spilt from a high temp.im no water heater expert but i would imagine the co2 levels if any wouldnt be productive to your grow.if they did put out a high ppm number there would be some law about having them inside living quarters.

Hello,
Appreciate the responses. I know that I don't know enough about water heaters. I also suspected that CO & CO2 are most likely completely vented through the roof.

It is currently in a corner and has one partition wall so it is, in effect, in a 3 walled, cubby hole. I expect I will put a door of some sort on the front, since there is occasionally a need to access it.