# Mr. C. Vleugels — Hazardous Materials Safety Interpretation

**Citation:** 99-0175  
**Type / status:** guidance / guidance  
**Agency:** Pipeline and Hazardous Materials Safety Administration  
**Effective:** Not stated  
**Published:** 1999-09-23

99-0175 concerning 171.8.

## Document text

<<<PAGE 1>>>

of Transportation
US. Department
Washington, D.C.
400 Seventh Street, S.W.
20590
Special Programs
Research and
Administration
SEP 2 3 1999
Mr. C. Vleugels
Ref. No. 99-0175
VanHool N.V.
Bernard Van Hoolstraat 58
B-2500 Lier Koningshooikt
Belgium
Dear Mr. Vleugels:
This is in response to your letter dated June 25, 1999, requesting clarification on determining whether
your material, Sodium Sulfide, UN 1849, is a "flowable" or a "non-flowable" solid as it relates to
provisions in § 173.32c (g)(2) of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-
180).
As used in § 173.32c(g)(2), a "flowable" solid is a solid material (e.g., crystal, powder, pellet, etc.) that.
moves in a smooth and uninterrupted movement through the valves of a tank. Sodium Sulfide in its
crystal or powder form is considered a "flowable" solid if it flows freely through the valves. A "non-
flowable" solid is a solid material in a cake or other solid form that does not flow in a smooth and
uninterrupted movement through the tank valves. If moisture affects your material causing clumping or
other solidification that interrupts free flow or movement through the valves of the tank; your material is
considered a "non-flowable" solid.
I hope this answers your inquiry.
Sincerely,
Delmer F. Billings
Chief, Standards Development
Office of Hazardous Materials Standards
990175

<<<PAGE 2>>>

99-0175
VANTOOL
Bus and trailer manufacturers
• Boothe .
171.8 Liquid
Department:
SB IV
US Department of Transportation US.
Solid
Contact:
Extension:
3414
Office of Hazardous Materials Standards
Our reference:
C. Vleugels
400 Seventh Street, S.W.
ET/CV/ds - 99/297
WASHINGTON D.C. 20590
USA
• For the attention of Mr. Billings
Lier, the 25th June, 1999
Your letter: ref. no. 22-0062
Dear Mr. Billings
. Could you please explain us how we can determine whether a cortain solid (UN 1849 -
Sodium Sulfide) is a "flowable" or a "non-flowable" solid, especially in the context of provi-
sion § 173.32c (g) (2).
We thank you in advance for your help and remain,
with kind regards
VAN HOOL N.V.
Reusele
C. VLEUGELS
TEE TARYAANS
al Manager
Van Hool N.V.

## Provenance

- Official: Yes
- Source: <https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/1999/990175.pdf>
- Source ID: `phmsa`
- SHA-256: `d810826cc8b4ef6126b825cabbda19ddda99700b29d8af978308ce89bd5d3278`
- Retrieved: 2026-08-20T00:59:31.977Z
- Exported: 2026-08-23T01:04:53.861Z
- Document slug: `phmsa-interpretation-99-0175`

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