Conclusion: No indications for effectiveness
A systematic review by Chalmers et al. (2004) concluded that for pool covers to be effective they need to be put in place when pools are not in use, which in practice may not always occur (Wintemute, 1992). Furthermore, in the case of covers designed to float on the surface of a pool, such as thermal blankets, the risk of undetected submersion may actually be increased (Harborview Injury Prevention and Research Centre, 1997; Sulkes and van der Jagt, 1990). It is argued that a toddler enticed onto a floating cover, by the appearance of a solid surface, may fall and become submerged beneath the cover.
A UK based study (Norris et al, 1994) concludes that the floating, heat retaining covers used on the majority of UK domestic pools possibly add to the intrinsic risks of a swimming pool. Winter debris covers, although appearing to seal the pool and considered by the majority of owners to make pools safer, were shown to allow children relatively easy access under the cover.
In line with Chalmers et al. and Norris et al, WHO guidelines on safe recreational use of swimming pools (2006) also conclude that pool covers have not been shown to be reliable preventive measures for very young children. In fact, the guidelines state, pool covers may themselves contribute to drowning - if they are not strong enough to hold the child's weight, the child could slip under the cover and be trapped by it, or the child could drown in small puddles of water formed on their surface. In addition, covers may delay the discovery of a drowning victim.
A recent technical report (Weiss et al, 2010) found no formal studies demonstrating the effectiveness of pool covers to prevent drowning in children. It concludes that retractable pool covers and pool nets capable of holding the weight of a child must be removed and replaced each time the pool is used and are not likely to be used appropriately and consistently. Because there has been no scientific study regarding the efficacy of pool covers, they cannot be recommended as a substitute for isolation fencing.
Conclusion on effectiveness: pool covers are no effective measure in preventing children in drowning, some types of pool covers actually present a hazard for children; some indications of potential danger.
Recommendations (for research & practice)
For policy and practice
WHO guidelines (2006): To prevent entrapment, it is recommended that the velocity of water flowing from the pool through outlets should not exceed 0.5 m/s and there should be a minimum of two outlets to each suction line. Also, outlets should be sized and located such that they cannot be blocked by the body of a single bather. Grilles in outlets should have gaps of less than 8 mm. In addition, pools and hot tubs should not be used if any of the covers are missing, unsecured or damaged.
Policy statement of American Academy of Pediatrics (AAP, 2010): Data regarding the value of pool covers are lacking. Although data are lacking, families can be advised to consider rigid pool covers as additional layers of protection; however, pool covers are no substitute for adequate fencing. It is important to note that some types of pool covers, such as thin plastic solar covers, should not be used as a means of protection, because children may try to walk on the cover, fall into the pool, and be hidden from the view.
The U.S. Consumer Product safety Commission (2009) states that power safety covers over the pool may be used as an alternative to door alarms. A power safety cover is a motor powered barrier that can be placed over the water area. Motor-driven covers easily open and close over the pool. When the power safety cover is properly in place over the pool, it provides a high level of safety for children under 5 years old by inhibiting their access to the water. A power safety cover should meet the requirements of the ASTM pool cover standard that addresses labeling requirements and performance. ASTM requires that a cover withstands the weight of two adults and a child to allow a rescue should an individual fall onto the cover. The standard also requires quick removal of water from the cover, as a young child can drown in just inches of water.
Gunatilaka et al (2004) searched the United States patent database and fould several inventions that attempt to overcome the danger of pool covers that cannot support a person's weight. These include pool covers that can support a person falling on them, a rising inflatable pool cover, an edge retainer for a floating pool cover that would prevent a child who falls or steps on the cover from falling into the water, and a pool cover made of strong lightweight panels.
For further research
Evidence review examining structural housing deficiencies, involving factors related to construction, design, installation, and lack of monitoring or maintenance, found that pool covers were interventions in need of formative research, both in efficacy and design (Jacobs et al, 2009; Di Guiseppi et al., 2010).
Review Date: 10/06/2011
Articles (reviews) and reports were included that were published between 1990 and 2010, in English and Dutch. The outcomes of the study were reviewed by the Dutch Consumer Safety Institute.
Strategy: An online literature search was performed by a researcher of the Consumer Safety Institute and after this a more thorough search was performed by the documentation centre of CSI (Catalog CenV, Pubmed, Injury lit, Google, Websites, 'Grey' literature). Results of each search were compared on differences and potential missed studies were added. First the titles and then abstracts were scanned in order to include relevant studies. In the case of insufficient information obtained from abstracts the full text articles were obtained. Relevant articles were scrutinized and background documents were created. In addition, relevant references of included articles were checked on new and relevant articles (i.e., snowball search).
The outcomes of the study were reviewed by an expert in the field of child safety in the summer of 2011.
Technical report : prevention of drowning (version 1.0)
Jeffrey Weiss (2010)
A survey of inventions aimed at preventing drowning : study report (version 1.0)
Ajith Gunatilaka, Joan Ozanne-Smith (2004)
The design and safety of swimming pool covers (version 1.0)
Beverly Norris, John R. Wilson (1994)
Policy statement - prevention of drowning (version 1.1)
Committee on injury, violence, and poison prevention (2010)
How to plan for the unexpected : preventing child drownings (version 1.0)
U.S. CPSC (0)
Housing interventions and health : a review of the evidence (version 1.0)
David E. Jacobs, Andrea Baeder (2009)
Drowning, near-drowning and other water-related injury : literature review and analysis of national injury data : report to accident compensation corporation (version 1.0)
David Chalmers, Brownwen McNoe, Shaun Stephenson, ... [et al.] (2004)
Guidelines for safe recreational water environments : volume 1. coastal and fresh-waters (version 1.0)
Housing interventions and control of injury-related structural deficiencies : a review of the evidence (version 1.0)
Carolyn DiGuiseppi, David E. Jacobs, Kieran J. Phelan ...[et al.] (2010)