One of the more difficult challenges for industrial hygienists and safety professionals involves the selection of chemical protective clothing for use when chemical and fire hazards are present at the same time. Such scenarios can include a single substance that is both toxic and flammable or multiple chemicals that share a combination of these hazardous properties. Dual chemical and fire hazards are common to refineries, petrochemical and other chemical plants, and even certain laboratory settings.  The key issue is that each hazard often requires different types of protection, and the protections may not always be compatible. For example, most materials used in traditional chemical-resistant garments are flammable. Some materials can even melt upon exposure to heat. Conversely, most materials used in traditional flame-resistant clothing offer little or no chemical protection. Compounding the problem, if chemical and flammable hazards are present at the same time, a traditional CR garment must not be worn over the top of or underneath a traditional FR suit.
Dual Hazard Protection
Selecting Protective Garments for Both Chemical Resistance and Flame Resistance 
Photo courtesy DowDuPont. The worker in the image is wearing the DuPont Tychem 6000, a single-hazard, chemical-resistant garment (non-FR version). View images of Tychem® 6000 FR.
Disadvantages of being unacclimatized:
  • Readily show signs of heat stress when exposed to hot environments.
  • Difficulty replacing all of the water lost in sweat.
  • Failure to replace the water lost will slow or prevent acclimatization.
Benefits of acclimatization:
  • Increased sweating efficiency (earlier onset of sweating, greater sweat production, and reduced electrolyte loss in sweat).
  • Stabilization of the circulation.
  • Work is performed with lower core temperature and heart rate.
  • Increased skin blood flow at a given core temperature.
Acclimatization plan:
  • Gradually increase exposure time in hot environmental conditions over a period of 7 to 14 days.
  • For new workers, the schedule should be no more than 20% of the usual duration of work in the hot environment on day 1 and a no more than 20% increase on each additional day.
  • For workers who have had previous experience with the job, the acclimatization regimen should be no more than 50% of the usual duration of work in the hot environment on day 1, 60% on day 2, 80% on day 3, and 100% on day 4.
  • The time required for non–physically fit individuals to develop acclimatization is about 50% greater than for the physically fit.
Level of acclimatization:
  • Relative to the initial level of physical fitness and the total heat stress experienced by the individual.
Maintaining acclimatization:
  • Can be maintained for a few days of non-heat exposure.
  • Absence from work in the heat for a week or more results in a significant loss in the beneficial adaptations leading to an increase likelihood of acute dehydration, illness, or fatigue.
  • Can be regained in 2 to 3 days upon return to a hot job.
  • Appears to be better maintained by those who are physically fit.
  • Seasonal shifts in temperatures may result in difficulties.
  • Working in hot, humid environments provides adaptive benefits that also apply in hot, desert environments, and vice versa.
  • Air conditioning will not affect acclimatization.
Acclimatization in Workers