Which standard is specifically for measuring carbon monoxide in ambient air?

The correct choice identifies ISO 4224 as the standard specifically designed for measuring carbon monoxide in ambient air. This standard provides a framework for the determination and evaluation of carbon monoxide levels in the atmosphere, ensuring that measurements are consistent, reliable, and in accordance with international guidelines for air quality.

This standard is particularly crucial because carbon monoxide is a harmful air pollutant that can pose significant health risks at elevated levels. By adhering to ISO 4224, organizations can effectively monitor ambient air quality and ensure compliance with environmental standards aimed at protecting public health.

In contrast, the other standards mentioned focus on different aspects or methodologies related to environmental measurements but do not specifically address the measurement of carbon monoxide in ambient air. ASTM D5149 is more related to emissions testing for various materials. The NIOSH Fume Exposure guideline primarily relates to occupational exposure limits rather than ambient air quality. British Standard 5228 deals with noise and vibration mitigation. Therefore, these choices do not directly pertain to the specific measurement of carbon monoxide in the ambient air context.