@solarslurpie Are these readings consistent over several days? Or is this a regular looking graph?
I asked Mr Google… During photosynthesis, plants absorb carbon dioxide and release oxygen. … Adding plants to interior spaces can increase oxygen levels. At night, photosynthesis ceases, and plants typically respire like humans, absorbing oxygen and releasing carbon dioxide.
From Encyclopedia Britannica… While most plants release oxygen during the day as part of photosynthesis, small amounts of carbon dioxide are emitted both day and night as a by-product of cellular respiration, The majority of plants also absorb carbon dioxide during the day for photosynthesis, and do so in greater amounts than what is released for cellular respiration.
The exception to this general rule are the plants (mostly cacti, bromeliads, and certain succulents) that rely on CAM photosynthesis and keep their leaf stomata closed during the day to reduce water loss. These plants do release some oxygen at night when the stomata open and the oxygen can escape.
Unless your intake is drawing in CO2 enriched air? Does look backwards tho!