As businesses in England begin to seek insurance coverage for revenue lost as a result of recent rioting, mid-market executives and business owners elsewhere might wonder how their business interruption coverage would respond to a sudden outbreak of civil unrest.

Mid-market companies can avoid battling their insurers over lost income in the event of a riot by thoroughly and regularly reviewing their policies and keeping tabs on the evolving nature of their total risk profile, including entities on both ends of the supply chain, experts say.

“Simply because a company loses income does not mean it has coverage for that loss,” warned Stevan Phillips, a partner with the Seattle-based law firm of Stoel Rives L.L.P.

Most mid-market companies have some form of business interruption coverage built into their commercial property policies that would respond to riot-related losses. Beyond income lost as a result of direct property damage, commercial property insurance also covers income lost due to restricted access to the property. In some cases, the coverage will pay employee wages in the event of a business interruption.

Separate insurance also is available for lost income due to utility service disruptions—primarily heating, cooling and electricity—and for losses by businesses that depend on the public's access to a nearby attraction, such as a stadium. But the parameters of coverage can vary depending on geography, industry and other factors.

“I am not sure there is a "standard' business interruption policy regarding civil unrest,” Mr. Phillips said. In civil unrest or large natural disasters, “there are a number of variations in policies which come into play.”

Claims for lost income due to restricted access tend to be the most problematic because policies contain specific, often confusing criteria for qualified claims, including provisions regarding the duration of loss, proximity to the affected area and nature of restricted access, experts say.

For example, losses are typically not covered if the company was barred from its premises for less than 24 hours, said David Brenner, a principal at Seattle-based law firm Riddell Williams P.S. Insurers also usually impose a limit on how far a claimant's property can be from the restricted zone for there to be coverage. The policyholder also needs to show that the government's closure of an area precluded access to their property.

“That's definitely something to watch out for when you're putting a policy together,” Mr. Brenner said, adding that many insurers switched from vague terms to more concrete mileage limits after the Sept. 11, 2001, terrorist attacks.

Since most policies cover only complete inaccessibility, firms with facilities indirectly affected or companies with the ability to conduct business remotely, may not be able to claim business interruption losses, he noted.

The nature of a government-ordered blockade or evacuation also can be significant in determining the validity of the claim, said John Hughes, a New York-based senior vp in the global property practice of Marsh Inc. Insurers often limit coverage to cases in which access is prohibited due to an immediate threat to people or property, but restrictions designed to protect a certain area from possible harm would likely be excluded, even if they occur within a policy's proximity allowance, he said.

Mid-market businesses with multiple locations in affected areas could be subject to separate deductibles if the insurer deems the losses separate occurrences, said Mike Lebovitz, a Johnston, R.I.-based senior vp at Affiliated FM Insurance Co. Additionally, many mid-market companies tend to lump multiple locations together on a policy, not specifically naming them, which could become problematic if such unnamed locations are hit, he added.

“Sometimes unnamed locations have different coverage than the named locations,” Mr. Lebovitz explained.

In addition to having a detailed knowledge of their local risks, mid-market companies should stay abreast of the risks posed to the entities on which they depend for both supplies and patronage, experts say.

Contingent business interruption coverage is available for companies worried that a disaster, whether natural or man-made, could render a key supplier or receiver incapable of conducting business. However, those policies carry many of the same restrictions as basic business interruption coverage, along with several limitations specific to the entities to be insured. Most insurers require companies to name the entities targeted in the coverage in advance and generally cover only “first-tier” suppliers and receivers.

“That would mean that your supplier is covered, but the supplier of your supplier is likely not included in the policy,” Mr. Brenner said.