## 1 Introduction  
### Heat Stress and Mitigation Techniques in Occupational Settings  
Workers in hot environments or those who are exposed to extreme heat may be at risk for heat stress [1]. Extreme heat poses a significant threat to workers and can result in decreased job efficiency, heightened risk of accidents, and a host of heat-related illnesses including life-threatening heat stroke [2]. There were 43 reported heat-related fatalities in the United States in 2019 [3]. While this figure represents a decrease from the peak of 61 deaths recorded in 2011, it remains higher than the majority of years between 2012 and 2018 [3]. The construction industry is a significant employer in the United States and construction workers make up a staggering 36% of all heat-related deaths in the workplace over the past 25 years, according to the Construction Research and Training (CPWR) [4]. Heat stress occurs when the body's core temperature rises to a level that exceeds its normal range (36.2-37.9 \({}^{\circ}\)C) [5], causing discomfort and potentially leading to more serious health conditions [1]. For example, [PERSON] et al. [6] explained that performing manual tasks in hot environments that cause heat stress and recurrent dehydration could lead to chronic kidney disease. The risk of heat-related illnesses, such as heat exhaustion and heat stroke, increases as temperatures rise, making it important for employers to monitor their employees' heat tolerance. Given current projections about global climate change and the increasing frequency of heat waves [6], the prevalence of heat-related illnesses in the workplace is expected to increase. Traditionally, heat stress risk is controlled by monitoring environmental factors such as humidity, air temperature, radiant heat sources, and air flow with a WetBulb Globe Temperature (WBGT) thermometer and heat stress meters [7]. [PERSON] et al. [8] explained that environmental factors and clothing worn by workers have been used to determine the likelihood of heat-related illnesses and to decide the most effective approach to controlling risk through the hierarchy of heat stress controls (listed in order of effectiveness: elimination or substitution, engineering controls, administrative controls, and personal protective equipment (PPE) [7]) or hygiene practices. Each strategy aims to prevent workers from being exposed to heat strain threshold limit value (TLV) as specified by the American Conference of Government and Industrial Hygiene (ACGIH). However, while this approach can provide an estimated predication of a worker's heat strain level, it cannot accurately determine the worker's real-time heat strain level in response to heat stress [8]. This is because workers have unique interindividual factors such as body mass index, gender, age, genetics, and health status, and intraindividual factors such as hydration status, work shift duration, sweat rate, heart rate, and medication usage [8]. In other words, different individuals may have different responses to heat stress, and the same individual may respond differently to heat stress under different conditions. These varying factors can lead to an inaccurate estimation of the worker's heat strain level, which could negatively impact their work productivity, safety [8], and ultimately result in financial loss for the employer. The risks associated with inaccurate heat strain estimates can be mitigated by considering both environmental factors and worker-specific factors such as physiological, psychophysical, and performance responses [8]. This requires a comprehensive assessment that considers individual factors that affect heat tolerance and sensitivity. Such assessments can help employers identify workers who may be at a higher risk of heat-related illnesses and implement appropriate interventions to prevent such illnesses. The development of wearable sensors for monitoring one or more physiological indicators, such as core body temperature, is gaining popularity [9].