A breath sampler for collecting a breath sample from a patient, the breath sampler comprising: a non-rebreather part comprising: a sample inlet; a one-way outlet valve arranged to allow air to exit the non-rebreather part, the one-way outlet valve and the sample inlet defining a first portion of an internal breath flow pathway therebetween; and an air inlet arranged to be closed by a one-way inlet valve arranged to allow air to enter the non-rebreather part, the air inlet being in fluid communication with the first portion of the internal breath flow pathway; and a sample delivery part in fluid communication with the non-rebreather part at an upstream end via the one-way outlet valve, the sample delivery part defining a second portion of the internal breath flow pathway, the sample delivery part comprising: an air diverter, in the sample delivery part, arranged to divide the sample delivery part into an upstream portion and a downstream portion; a sample outlet in the upstream portion; a return inlet in the downstream portion and in fluid communication with an exhaust; and a sample collection chamber connector configured to form a seal with an opening of a sample collection chamber, the connector defining a perimeter, the sample outlet and the return inlet being disposed within the perimeter; wherein the breath sampler further comprises the sample collection chamber coupled to the sample collection chamber connector, the sample collection chamber comprising a liquid capture interface, wherein the breath sampler is configured so that, during operation, the breath from the patient passes through the non-rebreather part, is delivered via the sample delivery part to the sample outlet into the sample collection chamber, passes through the liquid capture interface in the sample collection chamber which captures at least one of chemical markers and biological markers from the breath sample, the breath then re-enters the sample delivery part from the sample collection chamber via the return inlet, and escapes the breath sampler via the exhaust. a non-rebreather part comprising: a sample inlet; a one-way outlet valve arranged to allow air to exit the non-rebreather part, the one-way outlet valve and the sample inlet defining a first portion of an internal breath flow pathway therebetween; and an air inlet arranged to be closed by a one-way inlet valve arranged to allow air to enter the non-rebreather part, the air inlet being in fluid communication with the first portion of the internal breath flow pathway; and a sample inlet; a one-way outlet valve arranged to allow air to exit the non-rebreather part, the one-way outlet valve and the sample inlet defining a first portion of an internal breath flow pathway therebetween; and an air inlet arranged to be closed by a one-way inlet valve arranged to allow air to enter the non-rebreather part, the air inlet being in fluid communication with the first portion of the internal breath flow pathway; and a sample delivery part in fluid communication with the non-rebreather part at an upstream end via the one-way outlet valve, the sample delivery part defining a second portion of the internal breath flow pathway, the sample delivery part comprising: an air diverter, in the sample delivery part, arranged to divide the sample delivery part into an upstream portion and a downstream portion; a sample outlet in the upstream portion; a return inlet in the downstream portion and in fluid communication with an exhaust; and a sample collection chamber connector configured to form a seal with an opening of a sample collection chamber, the connector defining a perimeter, the sample outlet and the return inlet being disposed within the perimeter; an air diverter, in the sample delivery part, arranged to divide the sample delivery part into an upstream portion and a downstream portion; a sample outlet in the upstream portion; a return inlet in the downstream portion and in fluid communication with an exhaust; and a sample collection chamber connector configured to form a seal with an opening of a sample collection chamber, the connector defining a perimeter, the sample outlet and the return inlet being disposed within the perimeter; wherein the breath sampler further comprises the sample collection chamber coupled to the sample collection chamber connector, the sample collection chamber comprising a liquid capture interface, wherein the breath sampler is configured so that, during operation, the breath from the patient passes through the non-rebreather part, is delivered via the sample delivery part to the sample outlet into the sample collection chamber, passes through the liquid capture interface in the sample collection chamber which captures at least one of chemical markers and biological markers from the breath sample, the breath then re-enters the sample delivery part from the sample collection chamber via the return inlet, and escapes the breath sampler via the exhaust.