What is the maximum ERH for safe storage of durable commodities such as grain?
All durable products stored in bulk storage units can be stored safely at ERH level of 70% or lower. Some scientists prefer to specify storage at 65% ERHto provide for variations in instrument accuracy and product variations in storage compared to sample moisture readings. At 70% ERH , the moisture content and temperature of grain and other products will not sustain mold fungi development. Mold fungi varies in its water activity requirements. Some mold spores will not start growing below 75% and others below 80% ERH. Specific grain moisture contents and temperatures which are equivalent to 70% ERH vary significantly. Another term that is related to ERH is equilibrium moisture content (EMC) of grain and other stable or durable products. For example, according to ASAE Standards (1993) hard red winter (HRW) wheat has a 13.8% EMC at 70% RH and 77F (25C). At 60%RH and 77F, HRW wheat has an EMC of 12.1% moisture content. For yellow dent shelled corn at 77F and 70%RH , the EMC is 14.0%.
