An oxygen concentrator device comprising at least 2 separation vessels with a feed end and a product end, and a set of manifolds comprising at least one feed manifold attached to the feed end of the separation vessels and at least one equalization manifold attached to the product end of the separation vessels. The feed manifold comprises compression ports and valving; vacuum ports and valving; and, an upstream headspace equaling 2-6% of the total sorbent volume in the combined sieve beds. The equalization manifold comprises equalization ports and valving; and, a downstream headspace equaling 2-6% of the total sorbent volume in the combined sieve beds. The ratio of compression, vacuum, and equalization Cv to total sorbent volume is

[00001]$0.0005-0.005\left(\frac{\mathrm{gal}}{\min }\right)\left(\frac{1}{L_S}\right).$

Also, a method for concentrating oxygen, providing the set of manifolds described above and operating the oxygen concentrator without separately purging the sieve bed with an unused gas.