diff --git a/external/lab-hsa/spill/spill.md b/external/lab-hsa/spill/spill.md
index 9821e7a58f1f2064b0ad562d0d856f5b0f3e6474..12a9232d08f618a9672f6ff1d165600b85e03b83 100644
--- a/external/lab-hsa/spill/spill.md
+++ b/external/lab-hsa/spill/spill.md
@@ -72,7 +72,7 @@ You will find here below illustrations of interventions for chemical and biologi
 1. Wait 30min between the spill and the intervention. 
 2. Wear the appropriate PPE (refer to the safety datasheet).
 3. Plan your work and your sequence of operations to avoid contaminating yourself.
-4. Contain the spill with Trivorex.
+4. Contain the spill with Trivorex. Trivorex contains a pH indicator. It should turn yellow again once the chemical products are trapped.
 5. Sprinkle to cover the entire spill and wait for 10min.
 6. Remove with the shovel from the spill kit and discard it in a plastic bag that will be discarded in the blue bin with yellow cover (solids and liquids contaminated with biologicals and chemicals).