A reliable indicator of the air quality in offices, classrooms, or living rooms is the CO2 content. In fresh air, the concentration of carbon dioxide is around 400 ppm. This stands for “parts per ...
Since the launch of the Crossword in 1942, The Times has captivated solvers by providing engaging word and logic games. In 2014, we introduced the Mini Crossword — followed by Spelling Bee, Letter ...
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