Do you have an iPhone?
If so, download the following App's... 'Laser NOHD' and 'Laser Safety'
Both of which have been programmed by James Stewart at Laservisuals.
'Laser NOHD' should give you a good start at knowing at what distance your laser becomes eye safe for an accidental exposure... 1.8Watt Laser with a 1mr divergence becomes briefly eye safe (for 0.25 sec) at a distance of 300 mtrs.
Please note that these rough calculations are only a start and shouldn't be relied upon. There is no substitute for having the proper equipment and doing the 'real world' calculations.
Hope this helps.
Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.”... Douglas Adams 1952 - 2001