Airoux is within the urban area of Castelnaudary situated in the Lauragais on the Rigole de la plaine. It is located some 5 km north-west of Castelnaudary and 15 km south-east of Villefranche-de-Lauragais. It can be accessed on road D217 from Labastide-d'Anjou in the south through the village and continuing north-east to Soupex. There is also the D1 road from Montmaur in the northwest which also passes through the village and continues south-east to Ricaud. The commune consists entirely of farmland with no other villages or hamlets.
Numerous streams cover the entire commune with the Rigole of the Canal du Midi passing through the northern part of the commune and forming part of the northern border. An unnamed watercourse forms the whole western border between the rigole and the Fresquel river which forms the southern border of the commune. Numerous other unnamed streams and watercourses flow to the Fresquel from the commune to the south, south-east, and east.
In 2009, the commune had 3,682 inhabitants. The evolution of the number of inhabitants is known through the population censuses conducted in the commune since 1793. From the 21st century, a census of communes with fewer than 10,000 inhabitants is held every five years, unlike larger towns that have a sample survey every year.[Note 1]
The population of the municipality has 42.9% men and 57.1% women. This is generally older than the age groups of metropolitan France. There are 73 people under 20 years old for every 100 people over 60 years old giving an index of 0.73, while the index for French youth, which is equal to the division of the proportion under 20 years by the proportion over 60 years, is 1.06. The index for youth of the commune is also lower than the department (0.76) and that of the region (0.86).
Percentage Distribution of Age Groups in Airoux and Aude Department in 2009
^At the beginning of the 21st century, the methods of identification have been modified by law No. 2002-276 of 27 February 2002 , the so-called "law of local democracy" and in particular Title V "census operations" which allow, after a transitional period running from 2004 to 2008, the annual publication of the legal population of the different French administrative districts. For municipalities with a population greater than 10,000 inhabitants, a sample survey is conducted annually, the entire territory of these municipalities is taken into account at the end of the period of five years. The first "legal population" after 1999 under this new law came into force in 1 January 2009 and was based on the census of 2006.