The color change provides a presumptive test for the presence of protein. The more contamination present, the quicker the color change to purple and the darker the color. KEY FEATURES: Results in under 10 minutes. No instrumentation required - simple color-changing swab device detects 80μg protein after 1 minute. Detects 50μg protein after 5 minutes. Detects 20μg protein after 10 minutes. Results color chart printed on label for easy interpretation. Patented Snap-Valve technology and pre-moistened swab bud, "write-on" swab tube label. Instant results allow for immediate corrective action. No technical training required. Eighteen months shelf life.