IMS is scalable. This section explains how response organizations can shift from responding to small scale incidents to larger, more complex incidents and vice-versa.

The size of the response may be limited by the resources available to responders. Pre-existing agreements with partner organizations and jurisdictions can help expand response capacity when the needs of an incident go beyond the ability of an organization to respond alone.

The following factors can help incident responders make a decision to adjust the scale of the incident response structure:

  • increased or increasing safety risk to incident responders, members of the public, critical infrastructure, property and/or the environment
  • the size and complexity of the incident
  • concerns surrounding span of control

Incidents can be classified as a:

  • small incident (single organization): site response only
  • large incident (multiple organizations): site with optional EOC support
  • major incident: site(s) and EOCs support and with optional multi-organization coordination
  • local, provincial and national emergencies: site(s) or non-site specific with multiple EOCs and multi-organization coordination, spanning across a large region or provincially declared emergencies or federally declared national emergencies

(See Table 1: Response level criteria)

When does an incident become a complex incident?

Response escalation guidelines can help communities and organizations gather the amount of support and resources necessary to meet the needs of an incident. As an incident begins to include any of the factors described in Section 4.10 – Complex incidents, it becomes a complex incident. These factors can include multiple sites, multiple jurisdictions, mass casualties and/or a high demand for crisis communications.

A small incident requiring a single organization to respond is not a complex incident. The same applies in a large incident requiring multiple response organizations that would be considered as routine and easily managed by the response organizations. For example, firefighters would respond to a large house fire while paramedics would treat any injuries and police officers control the scene. In this example, the incident could easily be within the scope of ordinary operations for the response organizations involved and therefore, it is not a complex incident.

However, a large apartment fire resulting in mass casualties, impacting the daily life of the community and requiring the evacuation of residents is both a major and complex incident. All major incidents are complex incidents. All local, provincial and national level emergencies are also complex incidents.

Table 1: Response level criteria

Response levelSiteMultiple organizationsEOCMulti-organization coordinationMultiple EOCsMultiple sites/non-site specificComplex incidentAffecting whole regional area or provincial or federally declared emergency
1. Small incidentxN/AN/AN/AN/AN/AN/AN/A
2. Large incidentxxx
3. Major incidentxxxxxxxN/A
4. Local, provincial and national emergenciesxxxxxxxx

Various factors can cause an incident to escalate or de-escalate. Some incidents may occur as a local, provincial or national emergency and scale down where possible.

5.1 Small incident (single organization): site only

In a single organization response, there is a single line of command. Resources (personnel and equipment) come from one organization.

In this type of incident response, the first arriving responder becomes the incident commander. They are responsible for all of the IMS functions required for an incident response and should be prepared to activate additional functions as required. In a motor vehicle collision, there may be victims requiring medical attention, media agencies inquiring about the collision and other hazards that may be present. The incident commander is likely to assume some functions such as public information management and field inquiries from the media.

For the purposes of this document, the site may also be virtual and contained within one organization. For example, a local health clinic may detect a computer virus attempting to breach the patient record database however, the data is not compromised and patients are not affected.

If additional response organizations are required to manage an incident, the incident will escalate to a large incident (see Section 5.2 – Large incident (multiple organizations): Site with optional EOC support).

5.2 Large incident (multiple organizations): site with optional EOC support

If multiple organizations are required to respond to an incident, the incident will escalate from a single organization incident to a multi-organization incident. When this occurs, the incident management structure will need to expand to help the additional response organizations work together towards common incident objectives.

The incident commander must coordinate response activities across all incident response organizations. The incident commander should be a representative from the lead response organization and have the authority to make command-level decisions. For example, in a large explosion with multiple casualties, the incident commander (or unified command if necessary) coordinates multiple response organization activities such as search and rescue and site stabilization while protecting the safety of responders and the public.

The incident commander (or unified command if necessary) may appoint IMS section chiefs to help coordinate different functions effectively and efficiently. For instance, in the large explosion example above, the planning section will help plan for potential risks and suggest strategies on how to mitigate them. If the incident commander or section Chief(s) change, a detailed hand-over briefing is required (See Section 4.8 – Transfer of command).

An EOC may also be opened. There are various reasons to open an EOC. The incident commander may decide that the incident requires additional support. In this case, a community or organization may decide to open an EOC to provide support to resources at the site.

Multi-organization coordination

In some incidents, there may be more than one EOC involved. It is important for the EOCs involved to maintain regular communication and coordinate their actions. In some incidents, one EOC may act as the lead EOC. In other incidents such as widespread health incidents, unified coordination or a more collaborative network incident response structure may be more effective.

It is important to note that there may be multiple incident management teams operating beyond the site of an incident. For example, in the case of a shortage of a critical care drug, multi-organization coordination would be required to coordinate activities between hospitals, clinical care experts, ethicists, Health Canada and the Ministry of Health.


Communication with and between EOCs and response organizations is an important part of incident management. In a large incident involving multiple EOCs, a decision may be made to assign public information to one EOC. In this case, the assigned EOC may coordinate overall public information.

Incident responders and the organizations they represent need to be included in planning cycle meetings and at the incident command post. Where applicable, incident response organizations also need to maintain contact with the EOC either by phone, email or in-person. This helps all organizations involved in an incident to share information, support incident objectives and provide resources needed in the response.

If an incident no longer requires multiple organizations to support an incident response, it may be de-escalated to a small incident (see Section 5.1 – Small Incident (single organization): Site only). However, if an incident becomes complex or prolonged, the response may escalate to a major incident (see Section 5.3 – Major incident: Complex incident with site(s) and EOCs with optional multi-organization coordination (may be non-site specific).

5.3 Major incident: complex incident with site(s) and EOCs with optional multi-organization coordination (may be non-site specific)

A major incident can either be a large-scale or long-term incident. It will be a complex incident as described in Section 4.10 – Complex incidents. In a major incident, all IMS functions will likely need to be activated.

A complex incident with a large site may have to be divided into geographic sectors with a leader assigned to each sector. All leaders for the geographic sectors would then report to the incident commander at an incident command post. For incidents that may have multiple sites such as wildland fires, the incident response effort may need to be coordinated from area command.

In a large incident, IMS functional sections may be expanded to ensure an appropriate response. In a high-rise fire requiring an evacuation, the operations section would oversee fire suppression efforts and the evacuation of residents.

In a major incident, one or more EOCs will be necessary to provide incident support to the site(s).

In all incidents, an EOC should be opened when:

  • coordination, command and support to the site is required
  • multi-organization or multi-incident responses need additional coordination

It is important that the planning cycle includes regular communication between EOCs and the incident response organizations. The liaison officer plays an important role in communicating with outside communities, organizations and stakeholders (for more information about the liaison officer, see Section 6.2 – Coordination and command Staff (also known as command staff)). Coordination between organizations may also take place through multi-organization coordination.

Part of the planning cycle may include a formal reporting schedule. It is important for all communities and organizations involved in an incident response to collectively develop a plan to ensure that the incident response has the necessary resources (personnel and equipment). This should be part of building a written IAP.

As an incident is brought under control, the incident response may scale down. A long-term response may scale up and down several times depending on the nature of the incident and the response that is required. During a flooding event, the response may be scaled down as water levels return to normal but scaled up again if water levels start to increase. Scaling an incident up and down can also occur for technology-related incidents. For example, if an organization is scaling down as it recovers from a cyber-attack, the incident response may need to be scaled up if another cyber-attack occurs.

5.4 Local, provincial and national level emergency: complex incident affecting site(s) over a large geographic area or non-site specific with multiple EOCs and multi-organization coordination

A local, provincial and national level emergency is a complex incident with very serious or potentially catastrophic consequences to life safety, critical infrastructure, property and/or the environment. The duration of the incident response and/or recovery period in these large-scale incidents may last for an extended period of time. For example, a nuclear incident would fall into this response level.

A local, provincial and national level emergency is different from a major incident. For example, a high-rise fire may require local, provincial and/or federal support but is not an emergency affecting an entire local, provincial and/or federal jurisdiction. Local, provincial and national level emergencies may involve a large geographic area or may be non-site specific and have consequences which may affect a large geographic area. Local emergencies involve whole communities (towns, cities, municipalities or regions). A provincial emergency can affect a part of or the entire province and a national emergency can affect a part of or the entire country.

In a local, provincial and national level emergency, one or more EOCs are opened to coordinate multi-organization or multi-incident response between the respective sites. Incidents often begin as a locally managed response and a request for assistance from provincial ministries, federal departments and other organizations may be made. Scaling up an incident response level from local to provincial may be due to a request for assistance. On rare occasions, the incident response level may already be scaled up as a result of a provincial or a national declaration of an emergency.

In an incident where there are multiple sites:

  • each site has an incident commander with assigned response tasks
  • coordination and command is required between sites to avoid duplication of effort
  • area command may be established unless the site is so broad that an EOC is more appropriate to act as area command
  • the EOC should be informed of resource availability and requirements
  • area command or the EOC should ensure communications and support arrangements are in place and communicated across the various sites and incident response organizations

Non-site-specific incidents

In some cases, an incident may not have a defined site. Examples include system-wide incidents such as a pandemic or a cyber-attack. Responses to system-wide incidents:

  • are often collaborative, with coordination between partners rather than top-down decisions
  • are often coordinated through EOCs and by multi-organization coordination
  • may have international factors and be guided by international regulations

It should be noted that certain rare incidents require either provincial or federal management from the beginning of an incident. In Ontario, the provincial government has primary responsibility for coordinating the off-site effects and off-site response in a nuclear incident. At the national level, Transport Canada would respond to an incident involving Canadian airspace, as it is the statutory responsibility of the federal government.