What is the maximum CO2 level allowed in Grade D air?

The maximum allowable CO2 level in Grade D air is set at 1,000 parts per million (ppm), which translates to 1,000 ppn (parts per billion). The correct answer was indicated as 100 ppn, which is below the allowable limit. Therefore, based on the context of Grade D air quality, the appropriate choice relates to the 1,000 ppn threshold, not the 100 ppn listed. Grade D air standards are crucial for ensuring the safety of individuals in environments where respirators are used, as elevated levels of CO2 can lead to health risks. This standard helps maintain air quality for those in confined environments, especially in workplaces involving hazardous materials like asbestos.