Is there anything in the law that requires a service company to disclose the fact that a harmful substance can be emitted from a system that it installs?

You have a number of potential causes of action (claims) in a lawsuit against the service company and the manufacturer and seller of the product.  All of these parties would be named as defendants in a single lawsuit.

With regard to the service company, you could sue them for fraud.  Fraud is the misrepresentation of a material fact made with knowledge of its falsity and with the intent to induce your reliance upon which you justifiably relied to your damage.  In other words, you would not have purchased the UV light had you known that it would emit ozone.  Fraud also applies in cases of nondisclosure of a material fact which occurred here with the service company not informing you that ozone would be emitted by the light it installed and that you could not have reasonably discovered that fact.  You would also have claims against the service company for breach of warranty.  An express warranty is one that is in writing.  If there wasn't any express warranty since you said there wasn't any paperwork, you still have claims for breach of implied warranty of merchantability and breach of implied warranty of fitness for a particular purpose.  Implied warranties are unwritten.  Breach of implied warranty of merchantability means the product must be of an acceptable quality in the trade.  Breach of implied warranty of fitness for a particular purpose means that the product has to be fit for its particular purpose of in this case sanitizing the air.  You can argue that there is a breach of the implied warranty of fitness for a particular purpose because the product emits ozone and causes a health hazard.

If you are claiming that the product is defective, you could sue the manufacturer and seller of the product for negligence and strict liability.  Negligence is the failure to exercise due care, that degree of care that a reasonable manufacturer would have exercised under the same or similar circumstances to prevent foreseeable harm.  A manufacturer has a duty of care to produce a product that is not defective.  If the proiduct is inherently dangerous, then a warniing from the manufacturer should have been included with the product and you would have to argue that the warning would have prevented injury from the product.

Strict liability is liability whether or not due care was exercised.

The manufacturer and seller of the product are liable for negligence and strict liability.  The seller of the product is liable even if the seller could not have known that the product was defective.

Damages (the amount of compensation you are seeking in your lawsuit) Damages for fraud would be your out ot pocket loss (what you paid the service company )  Damages for breach of warranty would be replacement of the product or refund of the amount you paid the service company.  Damages for negligence and strict liability would be determined by medical bills, pain and suffering and wage loss caused by injury from the exposure to ozone.  Compensation for the medical bills is straight reimbursement.  Compensation for pain and suffering is an amount in addition to the medical bills based on the medical reports which document the nature and extent of the injury.  Compensation for wage loss is straight reimbursement.

With regard to the personal injury claims based on negligence and strict liability, each member of your family / household who was injured by the exposure to ozone would have a separate personal injury claim.