Quantum yields ϕ Δ of singlet oxygen ( 1 O 2 ) formation have been determined for 10 aryl azo naphtol dyes by flash photolysis. The 1 O 2 NIR luminescence signals at 1275nm sensitized by the dyes were compared with the signal obtained with the reference sensitizer, phenalenone. All aryl azo naphtols photosensitize the generation of 1 O 2 , but with very low quantum yields 4×10 −4 ≤ϕ Δ ≤5×10 −2 . Overall rate constants of 1 O 2 quenching could be determined for six of these dyes by flash photolysis. A linear correlation between the logarithms of these rate constants and the oxidation potentials of the quenchers could be established, thus indicating that quenching probably involves a charge-transfer mechanism. The roles of 1 O 2 on the photofading of azo dyes and on the photodegradation of consumer products are discussed.