Biofilters and oxidizers can be effective control devices to remove organic vapors that are hazardous air pollutants (HAPs) or volatile organic compounds (VOCs) from gas streams because they can convert toxic organic vapors into carbon dioxide and water. However, fluctuations in the vapor's concentration make it challenging for these devices to operate efficiently and economically. Combining adsorption with concentration and flow rate-controlled desorption provides an active buffer between the source of vapor and a secondary control device to more effectively remove the vapor from gas streams at a well defined concentration and total gas flow rate. Such approach can enhance the performance of the secondary control device by providing a stable concentration of vapor at a reduced total gas flow rate, which can result in a small more efficient secondary control device. Activated carbon fiber cloth (ACFC) was used with a bench-scale microwave swing adsorption (MSA) system and with an electrothermal swing adsorption (ESA) system to initially remove methyl ethyl ketone (MEK) from air streams. The MEK was then desorbed from the ACFC to provide readily controllable feed streams of MEK in air at a specified concentration and gas flow rate. MEK was adsorbed from air streams with a collection efficiency > 99.8% up to 5% breakthrough and was then desorbed at constant outlet concentrations between 170 ppmv and 5,000 ppmv. Total gas flow rate during the desorption cycle was 20% of the gas flow rate during the adsorption cycle. The systems then operated with the dynamic-tracking mode to demonstrate their ability to respond to a range of outlet concentration set-points between 170 ppmv and 5,000 ppmv. The controlled outlet concentration rapidly and accurately followed the concentration set-points. Such capability of the systems will allow secondary control devices such as a biofilter or an oxidizer to be optimized for tailored HAP and VOC concentrations and at a lower total gas flow rate that is not possible without such pretreatment.