Durability, a crucial parameter in determining the quality of a wood pellet, is affected by moisture adsorption from the air. The conditions in a confined space in which pellets are stored can be characterised as active or passive. In the active case, the interstitial air within the pile circulates around the pellets, whereas in the passive case, the interstitial air is stagnant. These two cases represent stored pellets in a ventilated silo (active) or in a ship's hold (passive). Commercial wood pellets were exposed to humid air in a humidity chamber with circulating air set at 95% relative humidity (RH) and 30 °C for up to 24 h. The wood pellets were also exposed to a range of RH values (11–90%) for four weeks, created using saturated salt solutions. The durability of pellets, volumetric swelling, and pellet density were measured. For pellets exposed to 95% RH, the durability of pellets, initially at 99%, dropped to below 80% after 10 h. A similar drop in durability was observed for pellets stored above saturated salt solutions but after a longer storage period. The density of pellets initially increased when pellets had a moisture content of 0.05–0.08 decimal dry basis (db). The pellets expanded by 20–80% volumetrically when the moisture content exceeded 0.15 (db), resulting in a marked decrease in pellet density.

耐久性是决定木质颗粒质量的关键参数，它会受到空气中水分的吸附。储存药丸的密闭空间中的条件可以表征为主动或被动。在主动情况下，堆中的间隙空气在药丸周围循环，而在被动情况下，间隙空气处于停滞状态。这两种情况表示在通风筒仓（主动式）或船舱（被动式）中存储的颗粒。将商用木屑颗粒暴露在潮湿室内的潮湿空气中，并将循环空气设置为95％相对湿度（RH）和30°C长达24小时。木质颗粒也要暴露于一定范围的相对湿度（11-90％）下，持续四个星期，这是使用饱和盐溶液制成的。测量颗粒的耐久性，体积溶胀和颗粒密度。对于暴露于95％RH的颗粒，颗粒的耐久性（最初为99％）在10小时后降至80％以下。对于储存在饱和盐溶液上方但经过较长储存时间的颗粒，观察到耐久性也有类似的下降。当小球的水分含量为0.05-0.08小数干基（db）时，小球的密度最初会增加。当水分含量超过0.15（db）时，颗粒的体积膨胀20-80％，导致颗粒密度显着降低。