Infants average 12 to 14 hours of sleep a day in their first three years of life. This long duration of sleep is what makes microenvironments a great concern; particularly those arising from the crib mattresses, which contribute to exposures of gaseous indoor air pollutants. An ordinary crib mattress is made up of petroleum-derived polyurethane, plastic materials, and assorted additives and adhesives. All of these materials indicate that the baby crib mattresses are a probable source of volatile organic compounds (VOCs). The objective of this study is to identify VOCs from crib mattresses and to measure the VOCs breathing zone (BZ) concentration in a large-scale chamber, while calculating the area-specific emission rate (SER) of VOCs from crib mattresses in small-scale chambers.
SER Experiment in Small-Scale Chambers.
Twenty crib mattresses in varying stages of use and composition were used in this investigation. These crib mattresses were cut into appropriate size samples to fit within the small-scale emission chambers. The chambers were then supplied with clean, purified air at 23±1 ºC and 50± 2% relative humidity (RH). The specific air-flow rate was 1.52 m/h, the same as the large-scale chamber experiments. All of this translates to a classic model of ventilation levels in a child’s bedroom. The air sampling was performed at the exhaust of the chamber, using sorbent tubes and a low-flow pump. 46 VOC experiments were performed, in total.
Large-Scale Chamber Experiments
New full-size mattresses and an infant thermal manikin were used in the large-scale analyses. The manikin was assembled using a hollow galvanized steel cylinder, with heating cylinders strategically placed inside. The surface temperature of the manikin was set to 35.6± 0.7 ºC., the approximate skin temperature of a sleeping infant. The large-scale emissions chamber was equipped with clean, purified air at 23± 1 ºC and 50± 2% RH (same as the small-scale experimentations). Three circumstances were considered upon testing: manikin heating on with a mattress cover, manikin heating on without mattress cover, manikin heating off without mattress cover. VOC concentrations were sampled concurrently at three locations using a stainless steel tubing and fittings. For a period of two to three days, four to six samples were taken for each of the three circumstances.
Small-Scale Chamber Results
All of the twenty crib mattresses were found to emit VOCs. A VOCs vapor pressure increases with temperature. This temperature dependence is especially important to the infant sleep microenvironments, because the heat released from a sleeping infant will warm surrounding objects, including their mattress. This concludes that VOC emissions will increase with the mattress’s surface temperature.
Large-Scale Chamber Results
The results proposed that there is a source-proximity effect related with the exposure of VOCs emitted from crib mattresses, due to the concentrations samples at the BZ being greater than the samples taken near the exhaust. Turning on the heat output of the manikin increased these VOCs BZ concentrations. VOCs sampled from the interior of the foam mattress were found to be in a greater enormity than the bulk of the outside air, indicating that the high pore absorption found in the materials of mattresses play an important role in infant exposure.
Image source: Flickr