Comment by edwintorok

Fira Sans is also one of the 3 free fonts (along with Charter and Source Code Pro) recommended by Butterick's Practical Typography: http://practicaltypography.com/

It is also used in Racket's documentation: http://typographica.org/typeface-reviews/fira-sans/

And here is how I use it in LaTeX:

  % Font settings
  \usepackage[T1]{fontenc}
  % Serif body font
  \usepackage{charter}
  % Math font
  \usepackage[charter]{mathdesign}
  % Monospaced font
  \usepackage{sourcecodepro}
  % Sans-serif font
  \usepackage[lf]{FiraSans}