Hoʻohana ka ʻōnaehana hoʻāʻo hoʻāʻo mamao ʻo Horizontal i ka ʻenehana absorption spectral e ʻike i ka hoʻokuʻu ʻana o carbon dioxide (CO2), carbon monoxide (CO), hydrocarbons (HC), a me nā nitrogen oxides (NOX) mai ka pau ʻana o ka kaʻa. Hoʻolālā ʻia ka ʻōnaehana no nā kaʻa ʻaila a me nā kaʻa diesel, a hiki ke ʻike i ka opacity, particulate matter (PM2.5), a me ka amonia (NH3) o nā kaʻa a me nā kaʻa diesel.
ʻO ka ʻōnaehana hoʻāʻo mamao mamao ʻo Horizontal kahi kumu kukui a me kahi ʻāpana kānana, kahi ʻāpana noʻonoʻo hoʻoneʻe ʻākau ʻākau, kahi ʻōnaehana loaʻa wikiwiki/wikiwiki, kahi ʻōnaehana ʻike kaʻa, kahi ʻōnaehana hoʻoili ʻikepili, kahi ʻōnaehana wela mau, kahi ʻōnaehana meteorological a me kahi. ʻāpana hana, hiki ke hoʻokele mamao ʻia ma o ka pūnaewele.