Work stoppages may be in violation of a contractual no-strike clause. The disciplinary action taken by a company is not usually subject to arbitration, but the question of the employees' action and the mitigating circumstance is. Employee work stoppages result from a perception of unsafe working conditions, employer contract violations, and employer disciplinary policies. The NLRB recognizes three reasons for strikes: economic, unfair labor practices, and those stoppages not defined by the National Labor Relations Act. In stoppages concerning working conditions, arbitrators usually consider the action exempt from no-strike clauses; the NLRB finds a statutory violation of Section 502 of the Act. Arbitrators have ruled hazardous plant conditions a mitigating factor while reducing or rejecting disciplinary actions. When a dispute arises concerning collective bargaining agreements, the NLRB distinguishes between interpretation disputes and contract breach in violation of the Act. The NLRB will conduct investigations about strike occurrences and unfair labor practices to determine if the activity is protected under the Act. Arbitrators tend to discount causal events and rule for the use of accepted grievance procedures. The causal event is also considered in actions involving employee discipline. Arbitrators only consider the work stoppage. Case citations and 28 footnotes are included.