September 23, 2019
By: Darrin Conlon, Director of Principal Engineers for Appliances, HVAC/R, and Lighting
Young children have been known to enter the drum of front-loading clothes washers and dryer, e.g., to play hide-and-seek, and some have died over the years due to suffocation. Child entrapment in a washer or dryer, while rare, still happens today. A child might climb into a machine, get trapped and suffocate because he or she can’t get out.
Therefore to mitigate the risk of child entrapment occurring, the UL Safety Standards for laundry appliances -- UL 2157, the Standard for Electric Clothes Washing Machines and Extractors, and UL 2158, the Standard for Electric Clothes Dryers, -- include entrapment requirements. These requirements are intended to mitigate the risk of suffocation that could lead to a child’s accidental death in the event that a child becomes trapped inside of a clothes washing machine or dryer.
UL 2157 and UL 2158 both provide three methods to comply with these entrapment requirements. A manufacturer can choose any one of these methods to evaluate their appliance to these entrapment requirements. One of these methods deals with the amount of ventilation that the appliance provides:
“If a household front-loading appliance has an opening into the clothes drum that will permit the entrance of a 203 mm diameter sphere and a clothes drum with a volume of 60 L or more, then the appliance shall be investigated with respect to the ventilation it provides."
UL Research & Development
UL’s Fire R&D team was requested to develop a test method to evaluate the amount of ventilation that a clothes washer or dryer provides. You may wonder why UL’s Fire R&D team was requested to conduct this type of work on these types of electrical appliances, where the particular risk prevention being studied was not related to a potential fire hazard. A large amount of fire protection research has reported the cumulative effects of decreasing oxygen and increasing carbon dioxide concentrations, as well as toxic substances, resulting from fires. This research was used to develop a test to evaluate ventilation, because people consume oxygen and release carbon dioxide similar to a very small fire.
The research objectives of the investigation were:
- Develop a simulation of an entrapped child, in terms of heat generation, oxygen consumption and carbon dioxide production.
- Develop a procedure to use the stimulation data in a representative clothes washer and dryer.
- Present hazard assessment information that may be used to establish acceptance limits.
- Develop a test method and compliance criteria for investigating an appliance, with respect to the ventilation it provides, that can be proposed to the UL Standards Technical Panel (STP) for future inclusion into the UL 2157 and UL 2158 Safety Standards.
A UL research project was designed to mimic the heat generation, oxygen consumption and carbon dioxide production of a child entrapped in either a clothes dryer or washer. A Bunsen burner using methane gas placed inside the drum of the appliance was used to stimulate the rate of oxygen consumption and heat generation. Carbon dioxide was added to the sample air in the drum to make up for the carbon dioxide production of a child.
Parameters were chosen to provide a range of values for oxygen consumption, carbon dioxide generation and heat generation (watts). A 6-year old boy in the 95th percentile weighing about 60 pounds was selected. This age of the child was chosen in order to displace the largest amount of air once the stimulated child is inside the washer or dryer. This stimulated child resulted in a displaced volume of 0.98 feet³.
Various references were consulted in order to specify the minimum rates of oxygen consumption and carbon dioxide production of a child.,, Purser has develop a fractional effective dose (FED) model that can be used to estimate the time to incapacitation due to increased carbon dioxide and decreased oxygen concentrations.
As a result of the research project, UL led a laundry appliance industry task group in the development of a standard revision proposal to revise both UL 2157 and UL 2158 to include a ventilation test requirement based on the UL research project. The proposal includes a test method to calculate the amount of ventilation a laundry appliances provides, determining the appropriate stimulated child to use, and the establishment of compliance criteria related to theoxygen and carbon dioxide levels intended to prevent suffocation.
The proposal was completed and was submitted to the UL 2157/UL 2158 Standards Technical Panel (STP) for review, comment and balloting for inclusion in these two laundry appliance standards. It is expected that these proposed requirements will be published in the next couple of years.
Using the output of UL’s research project to positively impact a UL Safety Standard and working with an industry task group have proven to be effective means to propose a change in requirements that are intended to increase the level of safety in these two UL Standards.
The proposed ventilation test method discussed above may also be applied to products other than laundry appliances. If there is product that includes a risk of child entrapment and suffocation, this requirement could be used to determine the amount of ventilation provided by that product.
For more information or questions regarding this topic, please contact Darrin Conlon at [email protected].
 Julia A. McMillan MD and Ralph David Feigin MD, Oski's Solution: Oski's Pediatrics: Principles and Practice, Fourth Edition, Apr 17, 2006, Ch 14 “Feeding the Healthy Child”
 Purser D.A. Assessment of Hazards to Occupants from Smoke, Toxic Gases and Heat. The SFPE Handbook of Fire Protection Engineering 4th ed), DiNenno P.J (ed.), National Fire Protection Association, Quincy, MA 02269, 2009, pp. 2/96 – 2/193.