Too much light

I’ve got two 1,000-watt HIDs in an area of 24 square feet. Is 290,000 lumens in 186 cubic feet (or 83 watts per square foot) too much light? Is there such thing as too much light? Is this safe for the plants?
Daniel A,
Alhambra, California

The plants can use the light providing they get enough nutrients, water and CO2. The plants are getting more light than they normally would indoors. This increases their rate of photosynthesis and their growth rate, so they require more nutrients. CO2, a gas found in the air, is used as an ingredient by plants in photosynthesis. With intense light, CO2 will become a limiting factor unless it is supplemented using a CO2 tank and regulator. About 350 parts per million (ppm) of CO2 is found in the air. In an active garden with little ventilation, it is quickly used up and photosynthesis is suspended. By enriching the air to 2,000 ppm CO2, photosynthesis will be supercharged and plant growth increases.

Another problem that you might face is excess heat. Using air-cooled light reflectors prevents heat from getting into the space. These reflectors are cooled by a stream of cool outside air.

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