Employees estimated heat release rates for these generators based on fuel consumption at 50% load, manufacturer specifications for generator tank capacity, gasoline heat of combustion of 42.5 MJ/kg, and assumed conservative engine thermal efficiency of 35%. Start printing of page 83568 Answer: The Commission does not believe that reducing CO emissions increases emissions of other pollutants. Based on emissions results from the prototype CPSC generator as well as those from the EPA demonstration program, reducing CO emission rates also results in reduced HC+NOX emissions. CPSC staff acknowledge that for the CPSC prototype, the ratio of lean airborne fuel to carburetor configuration resulted in increased exhaust temperatures. However, the rod notes that the muffler used was chosen in such a way as to allow the small catalytic converter to be easily integrated into it. This silencer had less internal confusion, resulting in average muffler surface temperatures about 70°C warmer than the OEM design. As a result, UA covered this silencer, resulting in lower fairing surface temperatures than the OEM muffler which was not sheathed. Staff note that the use of better designed silencers and, if necessary, improved cooling airflow on exhaust gases could mitigate the effects of increased exhaust temperatures. A: CPSC employees agree with Honda that lower fuel ratios generally lead to higher combustion temperatures.
The increase in the air-fuel ratio available for combustion was intended for the prototype engine in order to influence and reduce the mass flow of CO in exhaust emissions. For each emission test, cylinder head temperatures were measured in generator sets at all different load profiles. These emissions tests were performed before the engine modifications or durability tests, during the durability test, during which the engine operating hours were accumulated, and after the durability tests. Although the relationship is not absolute, physiological, epidemiological and clinical studies provide evidence that the acute effects of CO poisoning in healthy adults tend to follow toxicological dose-response principles, and that the risk of more serious adverse effects of CO poisoning gradually worsens as blood COHb levels increase. [46] However, it is clear that lethal exposures to CO cannot be defined simply by achieving a single level of COHb. Staff used several sources of information to develop COHb assessment criteria to assist in the calculation of estimates of anticipated benefits for producers with reduced CO emissions. A recent authorized review of CO toxicity by the Agency for Toxic Substances and Disease Registries shows that there is a high risk of fatal outcome once COHb levels reach a critical window, which is typically between 40% and 60% COHb for healthy individuals. [47] HS staff reviewed information on COHb levels from victims who suffered acute generator-related CO poisoning; Documented COHb concentrations in fatal CO poisoning reported to the CPSC were compared to reported COHb concentrations for a selected group of survivors who received hyperbaric oxygen therapy (HBO-T) for generator-related CO poisoning injuries that were considered high grade. Staff also considered information on lethal and non-lethal concentrations of COHb reported in non-fire CO poisoning cases that did not specifically involve generator-related CO exposures.
Based on a review of available data on COHb levels in lethal and non-lethal generator-related CO exposures and other non-generator and non-fire-related CO deaths and injuries, staff developed the following criteria to distinguish between modelled levels of COHb indicating fatal and non-fatal outcomes: Reaction: Cylinder heads, pistons and several other components are photographed and described in the section on Wear analysis was compared based on the durability of the contractor`s University of Alabama report. Description of the construction of a prototype portable generator with low carbon monoxide emissions and performance evaluation. Figure 22 of the UA report shows a direct comparison of the base generator cylinder heads (one unit unchanged) to the generator prototype after completion of the 500-hour durability test. CPSC employees partially agree with Honda`s photo rating because there are more visible carbon deposits on the prototype cylinder head gasket surface than on the same component in the baseline. However, the prototype cylinder head gasket survived approximately 585 engine hours from the durability program and subsequent emissions testing. According to the UA report, the head gasket of the base unit leaked after 175 hours of engine use during the durability test and was replaced. The cylinder head photos, which compared generator sets after the completion of the durability test and showed a lower carbon deposit on the head gasket seat of the base engine, can be explained by fewer engine hours accumulated on the new cylinder head gasket. In addition, staff note that at the time the photo was taken, the prototype engine had been operating for 585 hours, 85 hours longer than the manufacturer`s declared useful life of the engine. The Commission considers that none of the standards discussed in the previous section are adequate, as they do not address the hazard risk associated with CO beyond the reformulation of the CPSC labelling requirement, and the Commission does not consider that mandatory labelling requirements alone are sufficient to eliminate the risk.
Furthermore, the Commission is not aware of any company that certifies products to these standards. Therefore, the Commission considers that the standards are essentially not being met. Therefore, the Commission concludes that voluntary standards are not sufficient to address CO deaths and injuries. NIST compared the CO concentrations in the garage of the prototype and the unmodified carburetor generator after the same generator range during fully closed garage door testing. NIST found that the prototype had a 97 percent reduction in the amount of CO released into the garage, compared to the unmodified carburetor generator. This reduction is consistent with DU results and results in much lower CO transport throughout the home. Taking into account the time profile of the CO (i.e. , CO concentration over time) of each room in the house and garage, the Commission modelled the health effects and found that the prototype generator resulted in a significantly longer time interval for hypothetical residents to flee or be rescued before becoming unable to work. For example, in a test where the garage door and the connecting door to the house were closed, the time interval with the prototype was multiplied by 12 compared to the unmodified carburetor generator (from 8 minutes to 96 minutes) for the fatal scenario of a consumer in the garage with the generator.
The time interval increased even more for the residents of the house. CPSC staff developed a two-part technology demonstration program to demonstrate that the small spark-ignition engine powering a commercially available portable generator can be modified with existing emission control technology to reduce its CO emission rate to a level that should reduce the risk of fatal and severe CO poisoning.
