No one wants to experience a barn fire. In the past five years, there have been 42 human injuries and one human death related to barn fires reported by the Office of the Fire Marshal and Emergency Management (OFMEM).

When the origin of the fire is determined, approximately 40% of barn fires are caused by electrical system faults — the largest single cause of barn fires. Improvements in barn electrical system design, component choice and maintenance practices can help to drive down the number and cost of barn fires in Ontario.

This fact sheet provides information on:

  • how an electrical system can start a fire
  • which regulations apply to a barn's electrical system
  • design and component considerations
  • barn electrical maintenance practices

The operator is responsible for understanding these electrical safety requirements as well as other governing regulations on the farm.

Reducing the risk of barn electrical fires by following regular electrical inspections and maintenance by a licensed electrical contractor can result in reduced annual electrical system maintenance costs and insurance premiums.

Barn fire trends

Barn fires are devastating to the farmer due to the loss of livestock, crops, buildings, equipment and income. In 2019, the OFMEM reported 172 barn fires with estimated losses of over $47.3 million for buildings and equipment.

While the number of barn fires occurring per year has been decreasing in recent years (Figure 1), the average estimated dollar loss per barn fire has been increasing (Figure 2).

This figure is a line graph displaying the number of barn fires reported to the Office of the Fire Marshal and Emergency Management for the years from 2009 to 2019. The data shown is: 2009 = 211 barn fires, 2010 = 191 barn fires, 2011 = 209 barn fires, 2012 = 170 barn fires, 2013 = 178 barn fires and 2014 = 168 barn fires, 2015 = 190 barn fires, 2016 = 161 barn fires, 2017 = 164 barn fires, 2018 = 172 barn fires, 2019 = 172 barn fires. A trend line is included in the graph showing an overall reduction of approximately 20% over that period.
Figure 1. Barn fires with loss reported, per year, 2009 –2019.
Source: Ontario Fire Marshal and Emergency Management Data, 2021
This figure is a line graph displaying the average financial loss per barn fire for the years from 2009 to 2019. The financial loss includes the barn building, equipment and contents. The data shown is: 2009 = $129,000, 2010 = $159,000, 2011 = $175,000, 2012 = $110,000, 2013 = $190,000, 2014 = $178,000, 2015=$264,000, 2016 = $240,000, 2017 = $229,000, 2018 = $318,000 and 2019 = $275,000. A trendline is included in the graph showing an overall increase of approximately 20% over that period.
Figure 2. Average estimated loss per barn fire per year, 2009 to 2019.
Source: Ontario Fire Marshal and Emergency Management Data, 2021

Considering the significant personal and financial costs that can result from a barn fire, paying attention to the electrical system in the barn is an important activity that should be conducted at every farm in Ontario.

Effect of barn environment on electrical systems

The barn environment is harsh on electrical system components, especially in livestock and poultry operations. Livestock barn environments contain high humidity levels and elevated concentrations of corrosive gases such as hydrogen sulfide and ammonia. The combination of humidity and corrosive gas cause the copper in the barn electrical system to corrode at a much faster rate than the electrical system in the home. Rodent concentrations within the barn can cause damage to the electrical system and increase the risk of a barn fire.


Corrosion can cause two different fire ignition risks:

  1. Localized heat generation — As the surface of the copper wire or terminal in contact with the corrosive gas corrodes, the cross-section of the remaining copper becomes smaller. Electrical current travelling through the reduced copper cross-section responds by generating heat at that location. If sufficient deterioration of the copper occurs, the heat generated can reach the auto-ignition temperature of the surrounding materials. Once this temperature is reached, the surrounding material can spontaneously ignite (Figures 3 and 4).
  2. Arcing — Arcing can occur when corrosion has created a small gap between, for example, two terminals in an electrical system component. Stressed brass and copper can also crack when exposed to ammonia. In both of these cases, sparking occurs when an applied electrical current tries to jump across the gap. These sparks can ignite a fire in the surrounding materials
This is a photograph of a standard electrical receptacle which had been in use in a dairy barn. The receptacle has been split open to display severe corrosion of its internal copper components.
Figure 3. Corroded receptacle found in a dairy barn.
Source: Heartland Farm Mutual, Waterloo, Ontario.
This is a photograph of an electrical disconnect panel installed in a barn. The panel was operational at the time the photograph was taken. There is a large amount of cobwebs attached to the wall around the panel. The exterior of the panel is rusty. The access door of the panel is open to show heavily corroded disconnect switch components and fuses.
Figure 4. Corroded disconnect panel.
Source: Heartland Farm Mutual, Waterloo, Ontario.

Rodent damage

Rodents like to chew on the insulation coating on electrical cables in order to control the length of their continuously growing teeth. Arcing occurs when enough insulation is removed to expose two adjacent copper wires inside the cable (Figure 5). The arcing can ignite a fire in the adjacent materials.

This is a photograph of an electrical cable attached to a wooden beam inside a barn. The cable appears to be of an old style which uses woven insulation material. One section of the cable clearly shows evidence of rodent chewing damage. Rodents have chewed through all of the cables outer insulation and the internal conductor wires are visible.
Figure 5. Rodent damage on electrical cable.
Source: Heartland Farm Mutual, Waterloo, Ontario.

Humidity and pressure washing

Humid environments can also accelerate corrosion in barn electrical systems. Unless specifically addressed, the components in barn electrical systems are not designed to withstand the pressure and water flow associated with pressure washing of barn interiors and equipment. Water entering an electrical component (plug, receptacle, light fixture, light switch, etc.) can create short circuits, accelerate corrosion and cause other damage.

Regulatory environment

The Electrical Safety Authority (ESA) is mandated by the Government of Ontario to enhance public electrical safety in the province. It is both a safety regulator and advocate. ESA has responsibilities under the Electricity Act, 1998, and the Safety and Consumer Statutes Administration Act, 1996.

ESA's primary activities are identifying and targeting leading causes of electrical safety risk: monitoring and enforcing regulations; promoting awareness, education and training, and collaborating with stakeholders to improve the state of electrical safety in Ontario.

ESA recognizes the additional environmental risks impacting electrical systems installed in barns and provides guidance on acceptable electrical system installations in the following documents:

Ensuring a barn's electrical system complies with regulatory requirements is a good starting point to minimize the risk of barn fires caused by electrical system faults. A licensed electrical contractor is familiar with all the specific requirements of these regulations.

Barn electrical system design and components

When designing, modifying or updating a barn's electrical system:

  • It's the law that if you are hiring someone to do electrical work in Ontario, it must be a licensed electrical contractor. An ESA permit is required as it creates a permanent record of the electrical work that has been done and it triggers a review process by ESA. This is an added safeguard for the owner. When the work is complete, ask the licenced electrical contractor for the Certificate of Inspection to confirm the work was conducted in compliance with the OESC. Verify or find a licensed electrical contractor online.
  • The OESC and ESA Bulletin 22-3-* require that non-essential electrical equipment and electrical service distribution panels must be installed in locations separated from the livestock housing area of the barn. Install this equipment in a separate room which is supplied with clean, dry, temperature-controlled air. This will reduce the exposure of the electrical system components to the corrosive gases and moisture present in the livestock areas of the barn.
  • The OESC designates the type of wiring that must be used in barn electrical systems. For example, Non-Metallic Wet (NMW) or Non-Metallic Wet Underground (NMWU) cable must be used in livestock housing areas of barns. These designations indicate the cable insulation and outer coating is specifically designed for wet (NMW) or wet/underground (NMWU) conditions. Only copper cable is acceptable within the barn.
  • The OESC does not permit the installation of non-armoured cables behind walls, floors or ceiling panels unless installed in conduit (Figure 6). Concealed cables that are not mechanically protected are susceptible to rodent damage and cannot be inspected for condition.
  • The use of common receptacles, plugs and extension cords, in the livestock housing area of the barn have a heightened risk of starting a barn fire (Figure 7). The copper terminals in these components are continuously exposed to the wet, corrosive barn environment and can deteriorate quickly. The ESA Bulletin 22-3-* requires that equipment and lighting in this area of the barn must be hardwired wherever possible directly into sealed junction boxes (Figure 8). Where it isn't practical, wet-rated plug and receptacle connections such as those in Figure 9 must be used. This bulletin also dictates the use of anti-oxidizing paste on all wire connections to provide additional protection to the exposed copper.
  • Choose electrical system components which are specifically designed to operate in the barn environment. The OESC requires that the electrical system components used in the barn must be specifically designed to withstand the barn's corrosive and wet environment. There are different grades of electrical components available for different operating environments.
This is a photograph of a circuit breaker panel installed in a barn. The panel is of a style typically used for residential applications. The fuse panel access door has been removed and all the circuit breakers are exposed to the barn atmosphere. A large number of electrical cables exit the upper side of the circuit breaker panel. Most of these cables have been routed into holes drilled into the wall on which the panel in installed. Plastic conduit has not been used to protect the recessed wiring.
Figure 6. Recessed wiring.
Source: Heartland Farm Mutual, Waterloo, Ontario.
This is a photograph of three electrical motors mounted off the ceiling in a dairy barn. The three motors are all totally enclosed frames with integral cooling fans. Electrical power is supplied to motors through a common 220V plug inserted into a receptacle mounted on the ceiling. The receptacle is installed in a sealed plastic enclosure. The wiring supplying power to the receptacle is all installed in sealed plastic conduit.
Figure 7. Common plugs and receptacles are not recommended for use in barn environments.
Source: Heartland Farm Mutual, Waterloo, Ontario.
This is a photograph of the motor mounted off the ceiling in a dairy barn. A hardwired cable is supplying electricity to a junction box close by to the motor. A wet-rated plug and receptacle is used to supply electrical power from the junction box to the motor. The wet-rated plug and receptacle incorporates a seal to avoid the egress of water or corrosive gases into the plug and receptacle components.
Figure 8. Hard-wired compressor.
Source: Heartland Farm Mutual, Waterloo, Ontario
This is a photograph of a compressor installed inside a compressor room in a barn. There is an electrical disconnect panel installed on the wall of the room. The disconnect panel is rated for use in wet and dusty environments. The cable supplying electrical power from the disconnect panel to the compressor is hard-wired. A plug and receptacle is not used. Sealing grommets are installed around the cable to seal the point where it enters the compressor and disconnect panel.
Figure 9. Wet-rated plugs and receptacles with hard-wired cables are recommended for use in barn environments.
Source: Heartland Farm Mutual, Waterloo, Ontario.

The ability of electrical panels, junction boxes or disconnect switches to withstand dusty, wet and corrosive environments is indicated by their National Electric Manufacturers Association (NEMA) rating (Type 1 to Type 13) (Table 1). NEMA 1 and NEMA 2 are not appropriate for barn environments. The minimum rating for these components operating in a barn environment is a NEMA 3. Use components with a NEMA 4X rating in the livestock housing areas of the barn to withstand the wet and corrosive environment.

Table 1. NEMA ratings for electrical components
Source: National Electric Manufacturers Association
  • rated for outdoor use
  • no vents or holes in enclosure
  • gasket in door to protect against entry of dust and water
  • rated for outdoor use
  • no vents or holes in enclosure
  • plastic or stainless steel enclosure for corrosive environment
  • gasket in door to protect against entry of dust and water
  • rated for outdoor use
  • no vents or holes in enclosure
  • gasket in door to protect against entry of water during hose down
  • rated for outdoor use
  • no vents or holes in enclosure
  • plastic or stainless-steel enclosure for corrosive environment (Figure 10)
  • gasket in door to protect against entry of water during hose down
This is a photograph of a NEMA4X rated electrical enclosure mounted the wall of a barn. The enclosure is made out of grey plastic. There are no holes or vents in the enclosure that would allow moisture or corrosive gases to enter. The electrical wiring entering the enclosure is all housed in plastic conduit.
Figure 10. NEMA 4X rated enclosure.
Source: Heartland Farm Mutual, Waterloo, Ontario

Electrical system wiring and components designed to withstand the barn environment are more expensive than, for example, electrical wiring and switches designed to operate in residential houses. This can increase the cost of barn electrical system materials.

Using the right grade of electrical components, as specified in the Ontario Electrical Safety Code, can help to reduce the risk of a barn fire and maintain regulatory compliance for your operation. Considering the overall cost resulting from a barn fire it is not worth the risk to use the wrong electrical system components.

Best management practices

The OESC and ESA Bulletin 22-3-* establish minimum requirements for electrical safety. To further reduce risk, best management practices that go beyond regulatory requirements are identified. Consideration should be given to the following best practices:

  • Replace unprotected recessed wiring to minimize electrical safety risk. When replacement of the recessed wiring is not possible, install an arc fault circuit interrupter (AFCI) in the electrical supply panel to provide extra protection to these electrical circuits. An AFCI is a type of circuit breaker that is able to detect the condition of dangerous levels of electrical arcing within the circuit it protects. In comparison, conventional circuit breakers detect overload and short circuit conditions within an electrical circuit but not the presence of arcing. Arc faults are a leading cause of fires.
  • Electric motors used in barns should have a totally enclosed frame to protect against dust, water and corrosive gases entering the motor. Look for the designation Totally Enclosed Fan Cooled (TEFC), Totally Enclosed Non-Ventilated (TENV) or Totally Enclosed Air Over (TEAO) on the motor nameplate. Use electric motors with designation Totally Enclosed Wash Down (TEWD) when the motor will be subject to high pressure wash downs.
  • Electric box heaters installed in livestock barns are a specific area of concern. Many of these heaters are supplied with a plug already attached to the power supply cable. Heater installation using the supplied plug is not recommended due to the risk of corrosion on the plug and receptacle initiating a barn fire (Figure 11). In these cases, remove the plug and hardwire the heater power supply cable into a junction box with an appropriate NEMA rating for the installation location within the barn. If a plug and receptacle is required for maintenance purposes, use a wet-rated plug and receptacle set.
This is a photograph of box heater replaced from a barn. The yellow box heater is rusted and there is straw visible inside the heater housing. Electrical power was supplied to the heater through a cable and plug. The plug is being held up against the barn wall where it used to be installed. There is black burn marks on the plywood barn wall. The plug itself is heavily damaged. Its plastic housing is partially melted due to a fire that started within the plug and receptacle.
Figure 11. Fire started at box heater with receptacle and plug.
Source: Heartland Farm Mutual, Waterloo, Ontario

Additional barn activities

Some types of livestock barns are routinely washed several times during the year (for example, broiler chickens, weaner pigs, etc.) and the electrical equipment will be exposed to high pressure washers. To reduce risk of damage to electrical equipment:

  • Minimize the amount of electrical components present in the pressure wash area.
  • Ensure electrical components within the pressure wash area are rated to withstand high pressure wash down.
  • Provide additional protection to the electrical system by covering the electrical components with plastic sheets prior to the pressure wash down.

There will be times when temporary activities will occur within the barn that require electricity supply through extension cords. In these cases:

  • Ensure the extension cords are in good shape and contain wet rated plugs and receptacles.
  • Extension cords should only be used on a temporary basis as they are not safe for long term use.
  • Route the extension cord carefully to avoid the possibility of cable damage or immersion in water.
  • Where possible, remove combustible materials from the area of the activity.

Over-voltage is a condition where an electrical system receives short duration spikes of voltage, which are significantly higher than normal. This condition can damage electrical equipment. If there has been a history of inconsistent electrical power quality in the past, consider the following:

  • Contact the local hydro utility if any electrical power quality issues are noted.
  • A licensed electrical contractor can measure the quality of the electrical power being supplied to the barn and Install protective devices (for example, an over-voltage protection device) when needed.

The Ontario Ministry of Agriculture, Food and Rural Affairs Publication 837, Reducing the Risk of Fire on Your Farm, provides additional information on best practices to reduce barn fire risk.

Barn electrical system maintenance

Barn electrical systems are not maintenance-free systems. The effects of the barn environment as well as continuously changing barn activities imply the condition and loading of the electrical system is continuously changing as well. The electrical system requires regular attention.

Conduct a barn fire safety audit at least four times each year to identify and correct any factors that increase the risk of a barn fire. Look for the following:

  • Is there any visible evidence of damage, heat, arcing or excessive corrosion on the electrical system and surrounding materials? Hire a licensed electrical contractor immediately to correct any issues found.
  • Are there any extension cords or temporary electrical equipment in place (Figure 12)? Remove these items from the barn if not being used for a short-term, monitored activity.
  • Is there excessive flammable material being stored in close proximity to electrical system components (Figure 13)? If so, relocate the material to a safer location.
This is a photograph of an extension cord coiled and hanging on the wall inside a dairy barn. The extension cord is a light duty style intended for use in residential applications and not in a barn housing livestock. The extension cord has clearly been in use in that location for a long period of time.
Figure 12. Incorrect use of extension cords.
Source: Heartland Farm Mutual, Waterloo, Ontario.
This is a photograph of a light fixture installed in the straw storage area of a barn. The light fixture consists of an incandescent bulb screwed into a fixture base. The fixture base is hanging from the floor joist above by its electrical supply cable. There is no protective cover, screen or cage around the light bulb. There is straw and cobwebs directly surrounding the operating light bulb. There is a large quantity of loose straw being stored approximately 1 m directly below the light bulb.
Figure 13. Flammable material near light fixture.
Source: Heartland Farm Mutual, Waterloo, Ontario.

The barn electrical system, when under load, should be fully inspected by a licenced electrical contractor on an annual basis. A thermal scan of electrical system components using an infrared thermal scanner is very useful to identify hot spots which indicate the effects of corrosion (Figure 14). Many insurance companies provide this as a free service.

This is a photograph of an operator conducting an infrared thermal scan of an electrical panel inside a barn. The display screen of the infrared thermal scanner is visible in the photograph. The scanner displays its field of view in colors ranging from blue to white. The display color is related to temperature with blue being cool and white being hot. In this particular scan, most of the scanner display is pink in color. There are two electrical components in the center of the display which are white in color, indicating high localized heat.
Figure 14. Infrared thermal scan.
Source: Heartland Farm Mutual, Waterloo, Ontario.


Barn electrical system faults are a significant cause of barn fires each year. Focus on improving the electrical systems to ensure they are able to withstand the dusty, wet and corrosive environment within the barn. This will reduce the risk of a fire occurring. The Ontario Electrical Safety Code provides details on the required minimum system design practices and component choices to withstand the environmental challenges. Remember that barn electrical systems are not maintenance-free. Regular monitoring and a prompt response to issues found will keep the system in good shape. Hire only a licensed electrical contractor to do electrical work.


The information contained in this factsheet is not authoritative. It is derived from the 2015 Ontario Electrical Safety Code and Electrical Safety Authority Bulletin 22-3-* Electrical Equipment in Confinement Barns and is for information purposes only. Efforts have been made to make this factsheet as accurate as possible. In the event of a conflict, inconsistency or error, the requirements set out in the referenced legislation takes precedence. Do not rely on this fact sheet as a substitute for specialized legal or professional advice in connection with any particular matter. Although the fact sheet has been carefully written, the authors and the government of Ontario do not accept any legal responsibility for the contents of this fact sheet, including direct or indirect liability, arising from its use. Retain the services of a licenced electrical contractor to address any concerns with your barn's electrical system. This document does not intend to provide assurance of compliance with electrical safety regulations in Ontario. To receive assistance with compliance with electrical safety requirements or additional information on electrical safety, contact the Electrical Safety Authority.

This fact sheet was written by John Van de Vegte, P.Eng., OMAFRA, Dan Ward, P.Eng., OMAFRA and Steve Beadle, P.Eng., OMAFRA. It was reviewed by the Office of the Fire Marshal and Emergency Management, the Electrical Safety Authority and Heartland Farm Mutual.