Black substance in from my throat and nose when i blow or cough out spittle

[Dieudonnee]

It's been close to 2years that i started experiencing this black substance when i blow my nose. I have a feeling it's from the air conditioner in my office. I've had it cleaned/ serviced a couple of times because i think it's dirty but it persists (I don't use a/c at home) .
I'm pretty convinced about this being the source because if am away from the office for close to a week... i stop seeing it.
Kindly advice what this might be... if it's really the a/c or there's more to it.
I spoke to a doctor in my regular hospital and he gave a sample bottle to bring this over... but most times I only see it when i use the sink in the bathroom or use a hankerchief. I never got round to sending it to him.

Thanks for your advice.
Best regards.

[Dr Santos]

Hi D.,

Will look forward to your updates. A journal of sorts will also help you identify the possible triggers in your office that you could also avoid. Take care always!

[Dieudonnee]

Ok thanks... i'll do just that and let you know.

Rgds, D.

[Dr Santos]

Hi,
How are you? Are there other symptoms present?  I agree with your doctor that bringing a sample would help us determine the source of the substance.  The nose is composed of hair and other structures that filters the air for dirt and foreign substance that you breathe. If it does not appear if you are away from your office, then it is likely that the source is in your office.It is best that you have a sample of this first for proper evaluation. Take care and do keep us posted