en Occupational Health Original Article <div style="text-align: justify;"><span style="font-family:times new roman;"><strong>Background: </strong>Firefighting and rescue require high physical and psychological needs under unpredictable and dangerous conditions. Thus, this study aimed to investigate mental workload and affecting factors in firefighters.<br> <strong>Materials and Methods:</strong> This is a descriptive study which was conducted on 250 firefighters of Tehran, Iran. National Aeronautics and Space Administration Task Load Index (NASA-TLX) survey was used in order to evaluate the mental load among firefighters. This tool evaluates mental workload in 6 areas of mental need, physical need, time pressure, endeavor level, performance (efficiency) and disappointment level. Each area is investigated with a scale from zero to 100. Finally, data were analyzed using descriptive statistics, Pearson correlation test and linear regression.<br> <strong>Results</strong>: The mean and standard deviation (SD) of age in firefighters was 32.20 &plusmn; 4.54 years. The physical load dimension (93.48 &plusmn; 8.93) had highest value and disappointment and failure feeling (25.85 &plusmn; 23.38) had the lowest value in terms of mental workload. Association with educational level and the physical load was direct and significant (P = 0.035). None of the demographic variables including age, working history, educational level, marital status, as well as being smoker had an impact on total mental workload (P > 0.050).<br> <strong>Conclusions</strong>: Overall mental workload was high in firefighters which can influence working efficiency and increase errors in this occupational group. Hence, implementing effective programs for adjusting mental workload such as ergonomic and psychological interventions are recommended for reducing mental and psychological errors and stress.</span></div> Workload,Firefighters,National Aeronautics and Space Administration, 184 189 http://johe.rums.ac.ir/browse.php?a_code=A-10-243-2&slc_lang=en&sid=1 F Laal fereydoonlaal@gmail.com 22400319475328460010324 22400319475328460010324 No Student Research Committee, Dept. of Occupational Health, School of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Shahid Beheshti University of Medical Sciences MJ Jafari Jafari1952@yahoo.com 22400319475328460010325 22400319475328460010325 Yes Dept. of Occupational Health Engineering, Faculty of Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran. Shahid Beheshti University of Medical Sciences N Noorizadeh fereydoonlaal@gmail.com 22400319475328460010326 22400319475328460010326 No Dept. of Occupational Health, School of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran Shahid Beheshti University of Medical Sciences R Fallah Madvari fereydoonlaal@gmail.com 22400319475328460010327 22400319475328460010327 No Dept. of Occupational Health, Shahid Sadoughi University of Medical Sciences, Yazd, Iran. Shahid Sadoughi University of Medical Sciences E Rahimi fereydoonlaal@gmail.com 22400319475328460010328 22400319475328460010328 No Dept. of Public Health, Mamasani Higher Education Complex for Health, Shiraz University of Medical Sciences, Shiraz, Iran. Shiraz University of Medical Sciences E Ahmadi 22400319475328460010329 22400319475328460010329 No Birjand University, Birjand, Iran Birjand University