The invention relates to an apparatus (11) for analysing an exhaust gas of a vehicle, comprising a sample chamber (29) for receiving the exhaust gas, a heating device (24) for heating the exhaust gas provided to the sample chamber (29), and an infrared analysis device (23) having an infrared transmitter and an infrared receiver. The infrared transmitter is operable to transmit an infrared beam into the exhaust gas in the sample chamber (29), and the infrared receiver is operable to receive scattered infrared light from the exhaust gas in the sample chamber (29). The infrared analysis device (23) is operable to receive a signal from the infrared receiver and to compare it with a threshold level. A pass indication is issued if the exhaust gas is below the threshold level and a fail indication is issued if the exhaust gas is above the threshold level. The threshold level may correspond to a change in signal level equivalent to a predetermined density of particulates in the exhaust gas. The infrared receiver may be configured to generate the signal based on infrared light scattered from particles having a particle size preferably in the range 0.3 μm to 10 μm. Processing circuitry is preferably configured to operate the apparatus in a warm-up mode during a first period, during which the heater device (24) is activated. A fan (22), upstream of the sample chamber (29) and for delivering exhaust gas thereto, may be operated at one of a plurality of selectable fan speeds, the fan (22) being successively switched to higher ones of the selectable fan speeds. A method of analysing an exhaust gas is also disclosed.