From the article:

In the younger children aged 7.0 to 8.2 years with no exposure to molds or dampness, vitamin C administration increased the FEV1 level by 37% [forced expiratory volume per one second]. In the older children aged 8.3 to 10 years with exposure to molds or dampness in their bedroom more than one year before the study, vitamin C increased the FEV1 level by only 21%.