Willie Rennie accused ministers of taking an axe to any inch of political credibility after the figures emerged from a Freedom of Information request.
It asked what type of businesses were provided with funds through the Business Ventilation fund to undercut or raise non-fire doors and, secondly, how much was provided to each business to carry out this work.
With the Scottish Government having issued 42 awards, the figure now totals £19,200.
The Scottish Liberal Democrat economy spokesperson has now demanded more financial support for businesses, claiming the SNP had thrown good solutions “to the wind”.
He said: “The government’s humiliating foray into carpentry has taken an axe to their crumbling credibility.
“This ridiculous plan had no backing from medical guidance and triggered confusion and concern among the fire service.
“The Scottish Government should have been supporting businesses to invest in the installation of air filters and appropriate ventilation. Instead, this government has tossed effective responses and pragmatic solutions to the wind.
"The First Minister should announce fresh financial support so that businesses can install air filters, tackle Covid build up and support our path towards recovery.
“It would appear that the First Minister is hellbent on chopping, whether that be chopping up doors or chopping up the UK.”
Earlier this year the First Minister said £5 million of funding would be given to councils to allow them to take “whatever steps” necessary to improve air flow in classrooms.
It came after education secretary Shirley-Anne Somerville said about 2,000 classes needed improved ventilation, at an estimated cost of £4.3m.
This included £1.6m on air filters, £2.4m for mechanical fans and £300,000 for doors to be “undercut to increase air flow”.
Defending the policy at the time, Nicola Sturgeon said: "We’re not requiring local authorities to chop anything off of doors.
"We’re enabling local authorities, guided by health and safety considerations, to take the actions they consider necessary.
“If you have doors or windows that are not enabling that natural flow of air in a way that you would want it to, then it would strike me as basic common sense you would take measures to rectify that.
“What we’ve done is give additional money to local authorities to allow them to take whatever steps – air filtration systems, mechanical ventilation or basic rectification of the structure of classrooms – to improve the natural flow of air.”
A Scottish Government spokesperson said: “As part of the application process, businesses carried out their own self-assessment based on the needs of their individual premises – they decided what ventilation they required and proceeded with the works.
“For business premises that received awards, the most common items purchased were air filters, small mechanical vents and extractor fans, and standalone CO2 monitors.
“Only 3 per cent of items purchased related to businesses who chose to undercut or raise non-fire doors.”