What Is PCR Testing
PCR testing, or Polymerase Chain Reaction testing, is a laboratory method that identifies specific mold species by amplifying and detecting their DNA. Unlike culturing methods that take 5 to 10 days and may miss slow-growing species, PCR delivers results in 24 to 48 hours and can identify mold even if it's dead or non-viable. This matters because a property can harbor harmful mold that culture-based tests miss entirely.
How PCR Works for Mold
During mold inspection, your contractor collects dust samples, air samples, or material swabs from suspect areas. These samples go to a certified laboratory where technicians extract DNA from mold spores and cells. PCR equipment then copies specific mold DNA sequences millions of times, making them detectable even in tiny quantities. The result identifies the exact mold genus and often the species, such as Aspergillus fumigatus or Stachybotrys chartarum (black mold).
This precision is critical. Knowing you have Aspergillus rather than generic "Aspergillus-type mold" changes your remediation strategy. Some Aspergillus species produce aflatoxins; others do not. The EPA does not set specific exposure limits for mold, but identifying the species helps your remediation contractor understand toxicity risk and health impacts for occupants with respiratory conditions or compromised immune systems.
PCR vs. Other Testing Methods
- Culturing: Slower, misses non-viable mold, takes 5 to 10 days, less expensive upfront
- PCR: Faster, detects dead and alive mold, 24 to 48 hours, identifies species accurately, slightly higher cost
- ERMI testing: Measures 36 species simultaneously using PCR, useful for baseline indoor mold burden assessment
When to Use PCR Testing
Order PCR testing when you have visible mold or suspect hidden mold in walls, HVAC systems, or crawl spaces. It's especially useful if someone in your home has asthma, allergies, or immune issues. PCR results guide remediation scope. If testing identifies high concentrations of toxigenic species, you'll need containment protocols, professional removal, and moisture control to prevent recurrence.
After remediation, PCR testing confirms that mold levels dropped to acceptable ranges. The EPA recommends returning indoor mold to outdoor baseline levels, typically below 1,000 to 1,500 spores per cubic meter of air, though standards vary by region.
PCR Results and Moisture Control
PCR testing identifies the problem; fixing moisture eliminates it. High humidity above 60%, plumbing leaks, roof damage, and poor ventilation fuel mold growth. After remediation, control moisture by maintaining indoor humidity between 30 and 50%, fixing leaks within 24 to 48 hours, and ensuring proper drainage away from foundations. PCR testing 4 to 6 weeks post-remediation confirms your moisture control worked.
Common Questions
- How much does PCR mold testing cost? Expect $200 to $600 per sample depending on your lab and location. Multiple samples (different rooms or problem areas) add cost but provide better property assessment.
- Will PCR testing show me where mold is hiding? No. PCR identifies what's in a sample you provide. You or your inspector must collect samples from suspected areas. If you don't know where mold is, hire a certified mold inspector who uses moisture meters, thermal imaging, and visual inspection to pinpoint problem zones before sampling.
- Is PCR testing required by EPA guidelines? The EPA does not mandate mold testing. However, if you have visible mold, remediate it regardless of testing. Testing becomes valuable when mold is suspected but not visible, or when you need species identification to understand health risk and remediation scope.
Related Concepts
- ERMI (Environmental Relative Moldiness Index) uses PCR to measure 36 mold species and compare indoor levels to outdoor baseline
- Species Identification determines the exact mold type, which affects toxicity assessment and remediation approach