Laser ignition of stoichiometric mixture based on aluminum nanopowder and ammonium perchlorate were studied experimentally. The laser with a radiation wavelength of 1.06m and a pulse duration of 0.8 ms was used as a source of heat. The ignition thresholds were determined for open samples in the air and for samples confined with transparent dielectric. The difference in the obtained data is discussed within the thermal ignition theory.