Parts per million (ppm)
A measure of volume, of one substance inside of another. In cannabis growing, it’s often used to measure the amount of liquid nutrients in water used on plants. Cannabis plants can only absorb so many nutrients, so measuring the ppm and pH of water ensures plants get the correct amount of nutrients. PPM can also be used to measure the amount of CO2 in the air inside of an indoor grow space when using a CO2 burner.