Section 450.139 - Toxic hazards for flight(a)Applicability.(1) Except as specified in paragraph (a)(2), this section applies to any launch or reentry vehicle, including all vehicle components and payloads, that use toxic propellants or other toxic chemicals.(2) No toxic release hazard analysis is required for kerosene-based fuels, unless the Administrator determines that an analysis is required to protect public safety.(b)General. An operator must-(1) Conduct a toxic release hazard analysis in accordance with paragraph (c) of this section;(2) Manage the risk of casualties that could arise from the exposure to toxic release through one of the following means: (i) Contain hazards caused by toxic release in accordance with paragraph (d) of this section; or(ii) Perform a toxic risk assessment, in accordance with paragraph (e) of this section, that protects the public in compliance with the safety criteria of § 450.101 , including toxic release hazards.(3) Establish flight commit criteria based on the results of its toxic release hazard analysis and toxic containment or toxic risk assessment for any necessary evacuation of the public from any toxic hazard area.(c)Toxic release hazard analysis. A toxic release hazard analysis must- (1) Account for any toxic release that could occur during nominal or non-nominal flight;(2) Include a worst-case release scenario analysis or a maximum-credible release scenario analysis for each process that involves a toxic propellant or other chemical;(3) Determine if toxic release can occur based on an evaluation of the chemical compositions and quantities of propellants, other chemicals, vehicle materials, and projected combustion products, and the possible toxic release scenarios;(4) Account for both normal combustion products and any unreacted propellants and phase change or chemical derivatives of released substances; and(5) Account for any operational constraints and emergency procedures that provide protection from toxic release.(d)Toxic containment. An operator using toxic containment must manage the risk of any casualty from the exposure to toxic release either by-(1) Evacuating, or being prepared to evacuate, the public from any toxic hazard area in the event of a worst-case release or maximum-credible release scenario; or(2) Employing meteorological constraints to limit an operation to times during which prevailing winds and other conditions ensure that any member of the public would not be exposed to toxic concentrations and durations greater than accepted toxic thresholds for acute casualty in the event of a worst-case release or maximum-credible release scenario.(e)Toxic risk assessment. An operator using toxic risk assessment must establish flight commit criteria that demonstrate compliance with the safety criteria of § 450.101 . A toxic risk assessment must-(1) Account for airborne concentration and duration thresholds of toxic propellants or other chemicals. For any toxic propellant, other chemicals, or combustion product, an operator must use airborne toxic concentration and duration thresholds identified in a means of compliance accepted by the Administrator;(2) Account for physical phenomena expected to influence any toxic concentration and duration in the area surrounding the potential release site;(3) Determine a toxic hazard area for the launch or reentry, surrounding the potential release site for each toxic propellant or other chemical based on the amount and toxicity of the propellant or other chemical, the exposure duration, and the meteorological conditions involved;(4) Account for all members of the public who may be exposed to the toxic release, including all members of the public on land and on any waterborne vessels, populated offshore structures, and aircraft that are not operated in direct support of the launch or reentry; and(5) Account for any risk mitigation measures applied in the risk assessment.(f)Application requirements. An applicant must submit: (1) The identity of toxic propellant, chemical, or combustion products or derivatives in the possible toxic release;(2) The applicant's selected airborne toxic concentration and duration thresholds;(3) The meteorological conditions for the atmospheric transport and buoyant cloud rise of any toxic release from its source to downwind receptor locations;(4) Characterization of the terrain, as input for modeling the atmospheric transport of a toxic release from its source to downwind receptor locations;(5) The identity of the toxic dispersion model used, and any other input data;(6) Representative results of an applicant's toxic dispersion modeling to predict concentrations and durations at selected downwind receptor locations, to determine the toxic hazard area for a released quantity of the toxic substance;(7) A toxic release hazard analysis in accordance with paragraph (c) of this section: (i) A description of the failure modes and associated relative probabilities for potential toxic release scenarios used in the risk evaluation; and(ii) The methodology and representative results of an applicant's determination of the worst-case or maximum-credible quantity of any toxic release that might occur during the flight of a vehicle;(8) In accordance with § 450.139(b)(2) , (i) A toxic containment in accordance with paragraph (d) of this section, identify the evacuation plans or meteorological constraints and associated launch commit criteria needed to ensure that the public will not be within a toxic hazard area in the event of a worst-case release or maximum-credible release scenario; or(ii) A toxic risk assessment in accordance with paragraph (e) of this section:(A) A demonstration that the safety criteria in § 450.101 will be met;(B) The population characteristics in receptor locations that are identified by toxic dispersion modeling as toxic hazard areas;(C) A description of any risk mitigations applied in the toxic risk assessment; and(D) A description of the population exposure input data used in accordance with § 450.123 . Prescribed Hazard Controls for Safety-Critical Hardware and Computing Systems