There are various types of spirometers that use a number of different methods for measurement (pressure transducers, ultrasonic, water gauge).

Even with the numerical precision that a spirometer can provide, determining pulmonary function relies on differentiating the abnormal from the normal.

Traditionally, sources of variation have been understood in discrete categories, such as age, height, weight, gender, geographical region (altitude), and race or ethnicity.

Global efforts were made in the early twentieth century to standardize these sources to enable proper diagnosis and accurate evaluation of pulmonary function.

However, rather than further aiming to understand the causes of such variations, the primary approach for dealing with observed differences in lung capacity has been to "correct for" them.

Preconceived notions that 'white' people have greater pulmonary function are embedded in spirometer measurement interpretation and have only been reinforced through this medical stereotyping.

In this politically loaded context, in which new X-ray technology could not be fully trusted, the spirometer represented secure evidence of respiratory disease in numerical terms that could be used in the complex compensation network.

[11] Notably, spirometers have been used to evaluate vital capacity in India since 1929, recording a statistically significant difference between males (21.8 mL/cm) and females (18 mL/cm).

For example, Thomas Jefferson noted physical distinctions between different races such as a 'difference in the structure of the pulmonary apparatus,' which made black individuals 'more tolerant of heat and less so of cold, than the whites.

'[16] Jefferson's theories encouraged speculation on the natural conditioning of blacks for agricultural labor on southern plantations in the U.S.[17] Samuel Cartwright, a slavery apologist and plantation owner, used the spirometer to make the claim that black people consumed less oxygen than white people[18] in addition to racial 'peculiarities' he laid out in the New Orleans Medical and Surgical Journal that described racial differences in the respiratory system and the implication of them on labor.

Eustace H. Cluver conducted vital capacity measurement research at the University of Witwatersrand[20] and found that poor white people had physical unfitness but that it was attributable to environmental issues rather than genetics.

[21] Racism and the spirometer intersected again in these studies when further research was conducted on the effects of physical training on poor white recruits; vital capacity studies showed that 'the poor-white is biologically sound and can be turned into a valuable citizen'[22] but no comment was made on the outcome of black South Africans.

[26] Ideas connecting ethnicity to lack of nutrition and birthplace in a poor country become invalid as people immigrate to or may be born in richer nations.