Figuring out if a file is safe to open is hard to interpret. By using virus total you would not need to open the file and be vulnerable, you can just upload it to VirusTotal and check that way.
You can find out by seeing if Antivirus detect it. One of the best services for this is VirusTotal. It can be found on this page. This service will scan any file you upload with over 40 different antivirus companies and will show you the result. You can upload files up to 64MB in size and the entire process should only take about a minute.
The most difficult part of using VirusTotal is interpreting the results. It can sometimes be difficult to tell from the results whether a file is likely dangerous. In general, if a significant number of scanners show a warning the file is likely to be dangerous. However, even if only a few detect it that does not necessarily mean that it is safe. Below are example findings for two files that are indeed malicious.
Using VirusTotal does have a few drawbacks. One of these is that it is certainly possible for malware to be so new that not a single antivirus yet detects it. I have personally seen this on multiple occasions. Thus, even if VirusTotal shows that no Antivirus detects a file it does not mean that it is not dangerous.
If your analysis shows that a file is dangerous I would recommend that you submit it to as many anti-malware companies as possible. By following the steps outlined you can help prevent anyone else from being infected with that piece of malware, making the cyber world safe from 1 more virus.