Licence agreement

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  1. This licence agreement applies only to the SOFTWARE of the nv-calc (naturvents-calc) program.

  2. The firm VENTOSYSTEM Bohdan Kontrymowicz (VentosystemBK) is the Owner of the program and the Company maintains the legal copyright to this program.

  3. This program is dedicated to designers for calculation natural ventilation of workshops, specially industrial buildings with high thermal load. Any final reports produced with the assistance of this software may be included into the User’s projects, but in its original form only. No changes, especially those that do not credit the origin of the software’s ownership are allowed.

  4. This licence empower the User for legal use of the program after registration and activate account by the Owner.

  5. The login data to nv-calc (naturvents-calc) program in professional version can not be available to the third party (no registered) without Owners knowledge and agreement.

  6. Legal liability restrictions apply. The contents of these restrictions are displayed on program's homepage and also on the report of the calculation printout.

  7. VentosystemBK reserves the right to contact the User of the program in order to offer any additional or new information and obtain information on the use of the nv-calc program.


Formulas in this program are created to determine equilibrium between all thermal gains produced by industrial processes within a building as well as air flow exhausted by the ventilation system. Based on this principle, the program is not intended to calculate air exhaust used to prevent thermodynamic disasters such as fires or an explosion blast in the case of accidental discharge of flammable gases. This program requires the user to possess and apply engineering knowledge and to understand physical phenomena occurring in the natural ventilation of buildings. The results of the program’s calculations will always correspond to the adopted criteria and the input data which have been entered, for which only the user is responsible.

We cannot be held responsible the for the design assumptions and data / Legal liability disclaimer:

All data, information and theoretical assumptions for calculations used in our program have been carefully analyzed and verified by Ventosystem. However, the possibility of the occurrence of errors cannot be ruled out completely. Despite thorough verification we cannot be held responsible for the correctness, completeness and the ongoing pertinence of calculations results obtained on the basis of input data which were not authorized by VentosystemBK.

In particular, VentosystemBK is not responsible for any damage and consequences arising as a result of indirect or direct application of calculations which have not been authorized by us. VentosystemBK is not responsible for uncritical use of the results for applications which have not yet been tested. Please send remarks and suggestions for corrections to office@naturvents.com