Various embodiments include an exemplary design of a high-temperature condensation particle counter (HT-CPC) having particle-counting statistics that are greatly improved over prior art systems since the sample flow of the disclosed HT-CPC is at least eight times greater than the prior art systems. In one embodiment, the HT-CPC includes a saturator block to accept directly a sampled particle-laden gas flow, a condenser block located downstream and in fluid communication with the saturator block, an optics block located downstream and in fluid communication with the condenser block, and a makeup-flow block having a concentric-tube design located in fluid communication with and between the condenser block and the optics block. The makeup-flow block being configured to reduce volatile contents from re-nucleating in the optics block. Other designs and apparatuses are disclosed.