The research has been conducted to determine the safe residence time for people in a room where the composition of the gas environment has deteriorated due to fire. Carbon monoxide, which is produced by fire, has been found to be lethal for human life and health. Determination of safe time was made based on the study of the composition and amount of fire load in premises and buildings, physical and chemical properties of carbon monoxide, and its effect on the human body. The graphical dependences of the concentration of carbon monoxide in a room, as a function of time, were obtained for eight variants. The results allow authors to determine the possible residence time of a person in a building during a fire before the lethal concentration of carbon monoxide occurs. Studies made it possible to determine the safe residence time of people in a building on fire in a calculated way and to compare it with the normative indicators of the onset of lethal concentration of carbon monoxide in the air. The results obtained determine the safe time during which a person can escape from the building on fire.; Istraživanje je provedeno kako bi se utvrdilo koliko dugo ljudi mogu boraviti u prostoriji u kojoj je kakvoća zraka smanjena zbog požara. Ugljični monoksid, proizvod požara, jest smrtonosan i opasan za zdravlje. Sigurno vrijeme boravka utvrđeno je na temelju ispitivanja sastava i količine požarnog opterećenja u prostorijama i zgradama, fizikalnih i kemijskih svojstava ugljičnog monoksida i njegova djelovanja na ljudsko tijelo. Grafički je prikazana ovisnost koncentracije ugljičnog monoksida u prostoriji kao funkcije vremena, i to za osam varijanti. Rezultati omogućuju da se utvrdi moguće vrijeme boravka u zgradi tijekom požara prije nego dođe do smrtonosne koncentracije ugljičnog monoksida. Ispitivanjem je izračunato vrijeme sigurnog boravka u požarom zahvaćenoj zgradi te je moguća usporedba s normativnim pokazateljima dostizanja smrtonosne koncentracije ugljičnog dioksida u zraku. Rezultati služe za utvrđivanje sigurnog vremena za bijeg ljudi iz požarom zahvaćene zgrade.