Key health and fire hazards

Epoxy resins and hardeners are comprised of a number of chemical ingredients, of varying proportion and toxicity. They contain only a very small proportion of the more hazardous ingredients but it is still worth being aware of all potential hazards before starting to work with WEST SYSTEM® epoxy.

When we select raw ingredients for WEST SYSTEM epoxy products, we search for a balance between desired physical properties and lowest human and environmental health risks.

There is a safe exposure level for most substances. The more toxic the substance, the lower that level will be. Overexposure occurs when the safe exposure level is exceeded. When this happens, the substance can cause health problems. Your immune system and overall health can influence your tolerance of a substance.

Hazardous substances enter the body by skin absorption, inhalation or ingestion. The route for a particular substance depends on its physical characteristics and how it is normally used.

This page covers some key hazards epoxy users must be aware of:

Most common health hazards
Solvents: health hazards
Solvents and dust: fire hazards
Common workshop dusts: health hazards
Curing mixed epoxy: fire hazards

Most common health hazards

We have a long history of working with and around epoxies daily. As epoxy manufacturers, we have had a much higher risk of exposure to epoxy than the average builder or casual epoxy user. Through our own experience, and the experience of other builders, we can estimate the likelihood of health problems from handling WEST SYSTEM resins and hardeners.

The following are the most common health problems stemming from epoxy use. Nearly all of us can prevent these problems. The majority of those who do develop a health problem can continue using epoxy with adequate precautions.


Fewer than 10% of epoxy users react when overexposed to epoxy resin or hardener. The most common reaction is contact dermatitis, or skin inflammation. Both epoxy resin and hardener can cause acute contact dermatitis. Discomfort can be severe, but usually disappears after stopping contact with the irritant. Repeated skin contact with resins and hardeners may also cause chronic contact dermatitis, which is usually milder but longer lasting. If left untreated for long periods it can progress to eczema, a form of dermatitis that can include swelling, blisters and itching. Partially cured epoxy sanding dust, if allowed to settle on the skin, can also lead to contact dermatitis.

Allergic dermatitis (sensitisation)

Allergic dermatitis is a more serious problem, but less than 2% of epoxy users are likely to get it. Allergic dermatitis is when the body hyper-reacts to an allergen. Sensitisation is the condition of being allergic to a substance. Your immune system and the degree and frequency of exposure to epoxy affects your chance of becoming sensitised. You are most susceptible if you have been grossly overexposed to epoxy or if you are inherently sensitised or allergic to a component of epoxy. You are also more susceptible if you have fair skin, if you’ve already been exposed to other sensitising substances, or if you have hay fever, other allergies or are under stress.

You may become sensitised to epoxy after many exposures or just one. It could take ten days of exposure, a month, or even years. It is best to avoid all exposure because you cannot know ahead of time how much you can tolerate before you become allergic.

Allergic reactions to epoxy can result in irritated skin or respiratory problems. Irritated skin is by far the more common of the two. Usually, it appears much like a reaction to poison ivy and may include swelling, itching and red eyes. Just as with poison ivy, the irritation can be mild or severe, acute or chronic.

Inhaling concentrated epoxy vapours, if done frequently or for long periods, can irritate your respiratory tract. Exposing sensitive skin areas, like the eyelids, to highly concentrated epoxy vapours may cause itching and swelling.

See a doctor if irritation persists or worsens after avoiding epoxy for several days. There is no specific antidote for epoxy sensitisation, but symptoms can sometimes be treated with medicine.

Once sensitised, additional (and sometimes increasingly severe) reactions become likely upon future exposures, even to tiny amounts of epoxy. It is difficult, but not impossible to prevent recurrences. Resume epoxy use only after symptoms disappear, and strictly follow the recommended handling procedures to prevent exposure.

Severe irritation and chemical burns

Hardener burns are uncommon. Mixed epoxy is unlikely to cause burns. By themselves, WEST SYSTEM and PRO-SET epoxy hardeners are moderately corrosive. If left in contact with the skin, they can cause severe irritation and cause moderate chemical burns. Chemical burns develop gradually and first cause irritation and slight pain. The burn may discolour and slightly scar the skin. The time it takes for a hardener to cause a chemical burn depends on the area of contact and hardener concentration. When resin and hardener are mixed, the hardener is diluted and therefore less corrosive. Although mixed epoxy is less corrosive, never leave it on your skin. It cures rapidly and is difficult to remove.

Respiratory irritation

Breathing highly concentrated epoxy vapour can irritate the respiratory system and cause sensitisation. At room temperature, epoxy vapours are unlikely to be highly concentrated. However, if you are already sensitised to epoxy, exposure to low concentrations of epoxy vapours can trigger an allergic reaction. At warmer temperatures and in unventilated spaces, the epoxy vapour levels increase.

Never breathe the sanding dust of partially cured epoxy. Epoxy chemicals remain reactive until they have cured. Serious health problems can result from sanding epoxy before it is fully cured. When you inhale these dust particles, they become trapped in the mucus lining of your respiratory system. The reactive material can cause severe respiratory irritation and/or respiratory allergies.

WEST SYSTEM fillers present few hazards by themselves. However, breathing any nuisance dust will worsen existing respiratory problems. Smokers and others whose lungs are under strain are far more likely to develop serious respiratory problems.

Epoxy resins and hardeners: health hazards

The risk of exposure to resin, hardener and mixed epoxy is greatest when they are liquid. As epoxy cures, the chemical ingredients react to form a non-hazardous solid. As it solidifies, epoxy and its components are less likely to enter the body.

Skin contact is the most common means of exposure to resins and hardeners. Even minor skin contact, if repeated often enough, can cause chronic health problems. In rare cases, with prolonged or repeated contact, the skin can absorb harmful epoxy ingredients.

Exposure by inhaling vapours is unlikely, because epoxy products evaporate slowly. However, the risk increases when ventilation is inadequate or when the products are heated.

People rarely ingest epoxy, but it can happen when resin, hardener or mixed epoxy contaminates food, beverages or eating surfaces.

Solvents: health hazards

Many solvents pose serious health and safety hazards and the government is increasingly regulating worker exposure and overall usage.

Epoxy users commonly use solvents to dissolve epoxy from tools and to degrease surfaces before bonding. Solvents’ ability to dissolve and degrease is part of why they are hazardous to your health. They leach oils from the skin and break down protective fatty layers. This makes skin more susceptible to dermatitis. While dermatitis is the most common skin problem solvents cause, it doesn’t stop there.

Once solvents have penetrated the protective skin layers, they may quickly find their way into the blood stream. It is possible to absorb toxic amounts in this way. And if a solvent is used to clean epoxy from the skin, the skin can absorb both the solvent and the dissolved epoxy. This will intensify epoxy exposure.

Almost all solvents are toxic if you swallow, absorb or inhale enough. Solvents can irritate your respiratory system, eyes and skin. Some solvents may damage your heart, liver and other vital organs. Several solvents have been linked to cancer.

Repeatedly inhaling low to moderate levels of solvents can irritate the respiratory tract. Because of their drying effect, solvents can also interfere with the lungs' natural ability to clean themselves of impurities. When inhaled in high concentrations, solvents may depress the central nervous system. This is called narcosis. Symptoms of overexposure range from nausea and irritability to something that resembles alcohol intoxication. Continued overexposure to particularly toxic solvents can lead to loss of consciousness, permanent brain damage and death.

Some solvents give off a strong odour when highly concentrated, while others do not. Even for those that do, you may not notice the odour after you are exposed to it for a few hours, or if you have a cold. If you notice a strong odour while using a solvent, vapours may already be too highly concentrated and you will need to ventilate more or use a supplied-air respirator. Many milder solvents are being developed to replace the more hazardous solvents. If the manufacturer of solvent claims its product can be used on the skin, you should follow instructions carefully, and wash afterwards with warm, soapy water.

Solvents and dust: fire hazards

Most solvents are extremely flammable. By themselves, in paints, or other products, solvents cause many shop fires. The fire hazards that solvents pose may be their greatest threat, to both human health and property. You must follow basic shop safety rules whenever you use solvents. Research the flash points and evaporation rates, and use adequate ventilation. Remove all ignition sources.

An explosion can happen when solvent vapours mix with high concentrations of fine dust particles suspended in the air. Even by itself, wood dust is explosive. The finer the dust particle, the greater the chance of explosion. Also, as temperatures increase, an explosion can happen at lower solvent vapour concentrations. One worker, hand sanding, could not raise enough dust to cause an explosion, but several people operating power sanding equipment could.

An open flame can set off an explosion, as can an accidental charge of static electricity or a spark from a combustion engine, light switch or power tool. Some fine powders and fillers can generate enough static electricity to ignite a flammable atmosphere. When handling large quantities of powdered material, keep airborne concentrations to a minimum and use grounding devices on transfer equipment.

Common workshop dusts: health hazards

Sanding partially cured epoxy produces airborne dust. This can cause respiratory problems if inhaled, and dermatitis if allowed to settle on skin. Dust from fully cured epoxy is inert and considered a nuisance dust.

Although epoxy is firm enough to sand within two hours, it may not cure completely for up to two weeks. Until then, the dust can contain unreacted hazardous components. Do not overlook or underestimate this hazard.

Dusts from woods commonly used with epoxy, such as cedar, redwood, mahogany and teak, can cause allergic skin and respiratory reactions. Wood saps and oils contain irritants. These allergens are reduced as lumber dries, so it is always better to work with seasoned wood.

Dusts from minerals, such as asbestos and crystalline (not amorphous) silica are dangerous because of their shape, which makes them difficult to expel from the lungs. This is also true of airborne glass, carbon and similar fibres, coming from cutting and handling glass tape or cloth, or from sanding or grinding a fibreglass composite.

Use these materials only with adequate ventilation and appropriate respiratory protection, such as an approved particulate dust mask. For comfort and safety, avoid inhaling these dusts!

Curing mixed epoxy: fire hazards

The chemical reaction that cures mixed epoxy is exothermic. That means that it generates heat. If left to cure in a contained mass, such as in a mixing pot, it can generate enough heat to melt plastic, burn your skin or ignite surrounding combustible materials. The larger or thicker the epoxy mass, the more heat generated. A 100g mass of mixed epoxy can reach 200°C.

To prevent heat build-up, transfer epoxy from the mixing pot to a roller pan or other wide, shallow container. Fill large cavities with epoxy in multiple layers rather than in a single, thick layer. Heat build-up and uncontrolled curing are unlikely in typical bonding and coating jobs, because spreading the epoxy into thinner layers dissipates heat.

Mixed resin and hardener become hot and frothy as they thermally decompose, generating toxic vapours. These include carbon monoxide, oxides of nitrogen, ammonia, and possibly some aldehydes. Cured epoxy can emit similar vapours if you heat it too much. This can happen when you use a flame to release epoxy-mounted hardware. To reduce this risk, use just enough heat to release the hardware. Only as a last resort should you use a flame to burn epoxy from hardware. If you must do so, work in a well-ventilated area.

While leftover mixed epoxy cures, set the container aside where you can monitor it. Use a fan to disperse vapours and direct them away. Air purifying respirators may not be effective against these vapours.

Spontaneous combustion is a danger when hardeners are mixed with sawdust, wood chips, or other cellulosic materials. When hardener is spilled onto or mixed with sawdust, the air and moisture react with the amine to generate heat. If the heat is not dissipated quickly enough, it can ignite the sawdust. Do not use sawdust or other cellulosic materials to absorb a hardener spill. Likewise, do not pour unused hardener into a dustbin with sawdust or other cellulosic materials.

WEST SYSTEM epoxy resin and hardeners are classified non-flammable, because their flash points are greater than 100°C and they evaporate slowly. Furnaces, wood stoves, and other heat sources do not pose a serious fire hazard in the presence of epoxy vapours.

Material Safety Data Sheets
A Material Safety Data Sheet contains every safety detail you need about WEST SYSTEM epoxies and related products. And it also contains specific health and safety guidance. To request an MSDS for your WEST SYSTEM product, contact us.

This page covers all the fire and health hazards you should be aware of when using epoxy and other related products. We also recommend looking at these precautions to make sure your workshop and your use of WEST SYSTEM epoxy are completely safe. Find out more here.



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