Heat Gun Selection and Use in Research Labs

A heat gun is similar in appearance to a standard hairdryer, but is operated and used in a vastly different manner. Both are constructed with a motor-driven fan that blows air over an electrically heated filament.  The heating element in a heat gun typically becomes red-hot during use. Heat guns operate at lower air speeds and produce temperature as high as 1200F, hot enough to melt some types of glass.

Heat guns are frequently used in research labs to dry glassware, heat the upper parts of a distillation apparatus during distillation of high-boiling point materials, and to develop thin-layer chromatography (TLC) plates. Other applications for heat guns include:

• removing paint
• soldering
• curing epoxy resins
• removing ice accumulation
• heat shrink tubing application
• removing decals and stickers
• softening, molding and welding plastic materials
• accelerate evaporation

Basic heat guns have one heat setting and one fan speed and are designed primarily for paint stripping. More complicated models have two or three heat settings or variable adjustment within a range, together with a choice of two, three or variable speeds of air flow.

Although heat guns can produce extreme heat and are often used in lieu of a gas blow torch, the lack of a visible flame can create a false sense of security. The power switches and fan motors are not usually spark-free and can pose a serious ignition hazard. For these reasons, heat guns should never be used near flammable materials including open containers of flammable liquids, flammable vapors or hoods used to control flammable vapors.
             
Removing solvents and developing glass TLC plates is best done with a heat plate and forceps to manipulate the individual plates. When a heat plate is not available or insufficient for the procedure, a heat gun may be used. Never hold a sample without forceps while using a heat gun or you will risk direct exposure of the heat to your hand.

Developing TLC plates containing non-chlorinated solvents with a heat gun should be done on a benchtop clear of flammable and combustible materials, including paper towels,  books, solvents and other reagents. The amount of vapor created by the process will be minimal and should not create a hazard within the lab space. Developing TLC plates containing chlorinated or toxic solvents, or developing a large number of plates at one time should be done in a fume hood that is clear of flammable materials and free of a flammable atmosphere. 

While using a heat gun, the effective temperature of any heat gun can be reduced by holding it further away from the surface; however, always maintain a minimum of 1 cm of clearance between the outlet nozzle and the work surface. Having a heat gun with variable settings gives more choice and is preferred. Correct heat and air speed settings, if available, are determined by the type of work and pace best suited for the safety of the operator.

Do not use an extension cord to power a heat gun. Due to the high current draw, extension cords may overheat and pose a risk of a fire or electric shock. Never obstruct or cover the air inlet grills. If the air flow is reduced the heat gun will overheat and possible catch fire. Never operate the heat gun with the outlet nozzle directly against a surface, this will reduce the air flow and can have the same effect as obstructing the air inlet grills.

Safety considerations you should keep in mind when using a heat gun.

• Do not use a heat gun near combustible or flammable materials/atmospheres.
• Keep in mind the presence and direction of the heat produced
• Always switch the tool off before putting it down on any surface.
• Allow the tool to cool before storing it.
• Never touch the hot metal nozzle with clothing or skin.
• Never direct the air flow towards one’s body
• Do not look down the nozzle while the gun is turned on.
• Do not insert anything down the nozzle of the gun.
• Never block the inlet grill or obstruct the air flow of the unit while in operation

Accidents involving Heat Guns

Accidents have occurred at Princeton University due to improper use heat guns. The two most notable accidents involved heat guns used in the presence of flammable solvents resulting in extensive damage and property loss. 

• A laboratory worker was using a heat gun to heat approximately 0.5 liters of heptane in a Pyrex beaker by hand over an open bench. A splash of heptane came in contact with the elements of the heat gun, igniting the heptane and causing him to toss the beaker away from him. The sleeve of the worker's shirt caught fire. The flaming beaker landed on another work surface, spreading the fire to his computer. The worker immediately used a safety shower to put out the fire on his clothing, then used a fire extinguisher to put out the other fire. The worker received burns to his hand. The computer containing his thesis was destroyed.
   
• A laboratory worker was using a heat gun to accelerate evaporation of flammable solvent and develop thin-layer chromatography slides. Several stacks of paper towels, dispensing bottles of flammable solvent and 100 open vials of flammable solvent were in the fume hood where this process was carried out. The heat from the heat gun ignited the paper and vials of solvent, quickly spreading to the dispensing bottles which added more fuel to the fire.  Fortunately, the worker did not sustain any injuries; however, the damage caused to the fumehood and surrounding area was valued at over $32,000.00. The researcher’s reaction product was destroyed as well. The area of the lab involved in the incident was out of commission for several weeks.