Gas analyzers under 87441 measure composition through methods such as infrared absorption, electrochemical sensing, or paramagnetic detection without separating the gas mixture into components. Chromatographs (87442) physically separate mixture components before detection. An instrument that uses a separation column as part of its analytical process belongs in 87442 regardless of what it ultimately measures.

Portable single-gas or multi-gas detectors designed primarily for occupational safety monitoring—detecting toxic or combustible gases in the workplace—can fall under 87441 if their principal function is gas analysis. However, some safety detectors may be classified under alarm or safety equipment headings depending on their design and primary use; a classification review is advisable for devices that combine sensing with audible or visual alarm functions.